Because of that, we spent time this spring -- toward the start of the crisis in the US -- speaking to mayors about the vast challenges at the local level they were navigating. Their medical workers didn't have personal protective equipment, they didn't have tests and they were worried about hospital capacity.

These local leaders were also concerned about the physical, mental and economic health of the constituents who are also their friends and neighbors.

Now, almost five months in, we checked back with several of those mayors to see how the pandemic fight is going now. From the South, to the Midwest to the Northeast, there are still deep and common concerns. PPE is available but testing is still inadequate. Schools they never imagined would not resume in the fall are all struggling with how to do so safely in communities where case numbers are still high.

And, for some their biggest fear came true: Reopening parts of their cities too soon proved to be a mistake.

Tampa, Florida: 'Opening of the bars, that was a mistake'

Now she says a flaw in the statewide reopening plan fueled a resurgence in Covid-19 cases: opening Florida's bars.

"No one followed the rules from go," she said, noting people crowded bars, which she called "the veritable Petri dish for Covid-19."

Castor says they are scrambling to correct what she calls a "huge mistake" by sending law enforcement to crack down on "bad actors."

"We sent out a letter from our city attorney to over 100 bars and restaurants just reminding them of what the orders are now in the state of Florida and then any violations could result in a loss of a liquor license. So, that usually gets the bars' attention," Castor said.

Castor said she does not generally think the state, or her city, reopened too soon, despite the city enduring about 400 new coronavirus cases a day.

"We took the steps I think that we were thoughtful, and we were slow and deliberate," she said.

Still, things were so bad earlier this month, she put a mask mandate in place, which she said is starting to show positive results.

Last week the new case numbers had spiked to 900 a day in Tampa, which has a population of nearly 393,000 people. She says her mask ordinance combined with a "continued drumbeat" for people to socially distance, helped cut that number more than in half this week.

"I'm not making any excuses or trying to tie a bow around any of that. We're still in a very precarious spot. But one of the things proportionally that the number of deaths that we have is very, very low for the number of cases," Castor says.

But testing remains a problem in Tampa just as it does around the country. It is more available than before but results often take up to 10 days to process.

When we spoke in early April, Castor, who was Tampa's police chief for three decades, told us that in all of her years of law enforcement and emergency management, she had never seen this kind of unpreparedness from the federal government.

"That statement still holds true," Castor told us this week. "There's just a complete lack of leadership or direction on the federal level in this particular incident."

One of the big ripple effects on Tampa, as it is nationwide, is uncertainty about reopening schools. DeSantis wants them to open, but she says Tampa's superintendent is giving parents a choice.

"Kids can stay home and go through the e-learning that they've been using all summer. They can respond to the classroom. My instinct tells me that the schools aren't going to open on time, that there'd be an actual delay," she said.

Waterloo, Iowa: 'We're not out of the woods yet'

Tysons had indefinitely suspended production at the plant where more than 1,000 workers became infected. Now, the plant is open with increased safety measures including on-site testing and social distancing.

Hart, a Democrat, said it's "doing pretty well."

"We're happy and we're pleased about that. And that's also reflected in our numbers too. ... We were seeing hundreds of people per day, well into 50, 60 people per day. Now it may be seven, it may be six, it may be less," he said.

But Hart is not convinced his city is out of the woods yet, as state and county numbers continue to rise.

"We are very cautious because we don't want to move too fast and refer to where we're like some of the other states that are now open too fast, did things too soon but now have to scale back things," Hart says.

He is strongly encouraging his citizens to wear masks, but he is not considering implementing a mandatory mask mandate like the one just put in place in Iowa City.

Iowa Gov. Kim Reynolds, a Republican, has said cities do not have the authority to do so.

"I think it's incredible where mayors are able to make the best decisions for their individual communities. The way we deal with it is not a cookie cutter situation in how we enforce things," he said.

"Mayors need to have the discretion to be able to have nonpolitical, non-biased opportunities to lead their communities, and not have that disrupted by governors and federal officials. We need to be able to have home rule," he added.

Not listening to local leaders, Hart believes, is where the state and federal governments went wrong during the peak of Waterloo's outbreak in April.

"I feel that if they would have listened to us locally, sooner, than us having to go on television and write a myriad of different letters ... then we wouldn't have had near the amount of cases we had," the mayor said.

All things considered, Hart says he is proud of the way his city locally managed the outbreak, and he attributes some of their success to being proactive on the public health side.

"Pro-business means pro-worker means pro-public health. That's the way we approach this. We don't have it all solved, but we're talking a lot more and communicating upfront," the mayor said.

As the debate about reopening schools continues nationwide, Reynolds issued a proclamation saying 50% of schooling needs to be in person, which Hart calls a "huge concern."

"You may have districts that have teachers and administrators that are susceptible and vulnerable populations. And so, you're basically forcing these people to go back into a situation where they may lose their life from if they contracted Covid. So, that's a challenge," Hart said.

Hart is no stranger to the concerns of educators and students returning to school. His wife is a vice principal at a local elementary school, and he has young children at home. Waterloo's school system will begin with a phased opening.

"There is going to be the option of parents to be able to do some online learning. But as we know, there may be a lot of parents out there that can't stay home and work from home while they do education," he explained.

He thinks it will be hard for schools to follow US Centers for Disease Control and Prevention guidelines of staying six feet apart, but says the schools are trying to erect dividers between desks, provide masks and put a contact tracing system in place.

Hart, the first black mayor of his city, says the list of what keeps him up at night keeps growing.

"It was Tyson, then it was Covid, but then it was also with the Black Lives Matter movement," he said.

"I would probably say trying to figure out what we can do better keeps me up, and that is still Covid, that is still police-community relations, that is still trying to get economic development to areas that need it," he added.

He said the past six months have completely changed his life and created a new normal within his community and he is trying to adapt.

"Still show good, humble leadership in these times," he said.

Topeka, Kansas: 'Our community is starting to see how serious it is'

"We actually recently had a few public figures in our community having the virus, and just yesterday, one of our council members, our deputy mayor, was talking about the challenges that he has. And I'm hopeful that these are the conversations that are helping us understand that the virus is serious," De La Isla, a Democrat, told CNN in a phone interview.

Topeka's cases are climbing, but because she believes her residents are finally practicing social distancing and wearing masks, she is hoping the trend will reverse. There are signs that could happen -- the city saw its first drop in the number of cases on Wednesday.

Topeka has not seen case numbers anywhere near as high as hotspots nationwide. They average between 15 and 20 new cases each day, according to De La Isla. She thinks the executive order that Kansas Gov. Laura Kelly, a fellow Democrat, put in place in early July requiring masks statewide has made all the difference.

"Overall, we are very fortunate that the governor was wise enough to request the use of masks by everybody in the state because the numbers in the state started to go up, and I can tell you that I think it's starting to work. It's been a week, and we are finally seeing our first drop in our chart," she explained.

De La Isla also praised the governor's push for more testing statewide, which has allowed her to have more free testing for individuals in her community. Her state still falls on the lower end of testing per capita, and De La Isla is concerned test results are taking too long.

"I think that we are starting to overwhelm the system, and sometimes the testing is coming back four to five days after testing," she said.

Her city is now in Phase 3 of reopening, and she worries her constituents are exhausted by all of the precautions to protect themselves against Covid-19.

"Our joke here has been that we are in phase 3.4 of people feeling that we're OK. ... There is absolutely fatigue," she said.

The mental health of her constituents has been a top priority for De La Isla since the pandemic began. When we spoke in April, she had found creative ways to connect with her residents and provide emotional support, like starting a "warm line" (instead of hot line) for people in distress, and reading to children on Facebook every Sunday, which she still does.

As a single mom, De La Isla is having to make the same tough decision that parents across the nation are facing whether her two teen daughters will return to school in the fall.

"Does it worry me? Of course. I don't want my daughters to get sick. I don't want to get sick, but I'm hopeful that the school districts will come up with a plan that will include social distancing entry and exit strategies, as well as mass protection, and the proper protocol so that if somebody ends up sick, that we all understand how to do this," she said.

Kelly issued an executive order that would delay the start of the school year for a few weeks until September 8, but the Kansas State Board of Education rejected the order this week.

But some school districts, like Topeka, already plan to open in September with a phased approach beginning with all virtual learning.

De La Isla says her daughters want to go back to school.

"I can tell you that for my oldest daughter, she likes the online classes. She did very well in them. My youngest daughter had a really hard time with online learning. She's a social creature. She enjoys the camaraderie of her teachers and her classmates, and she was very demoralized. Both of them are dying for school to start back up," De La Isla said.

When we asked De La Isla back in April what keeps her up at night, she said it was whether doctors will have enough equipment if the virus hits her city hard, and whether the city's hospitals will have enough beds.

For now, her city is managing on both fronts, but her worries have shifted

"I firmly believe that we are at the intersection of 1918, with the pandemic, and 1968, with the civil arrest demonstrations that we had across the nation," she said.

De La Isla wants to make sure everyone in her community feels safe, "regardless of the color of their skin or who they worship and who they love." And as mayor, she needs to balance that with the demands of Covid and maintaining their city's ability to "test everybody that needs testing, so that we can continue moving our economy forward."

The emotions of her job are sometimes too much for her to contain.

"A few weeks ago, after the George Floyd incidents, I was pretty transparent. I was crying in the TV when I was telling everybody that I was not OK. That the weight of what's happening nationally combined with Covid, it's a lot for anybody to handle," the mayor said.

"It's just a very challenging time to be a mayor and know that you are responsible for the wellbeing of a whole community, and understanding and working every single day, face-to-face with these challenges. Just check on your mayors. Seriously, just check in on your mayors because we're carrying a lot of burden," she added.

Philadelphia: "We want federal help, but not that kind of federal help"

Nearly half of all Philadelphia coronavirus cases are African Americans. No other group even comes close.

"That represents the disparity in all of our society. Medical care, medical access, access to medical care has been poor for people of color. Systemic racism has put them in situations where, not only are they more likely to get Covid or die from Covid, but also diabetes and heart disease," Kenney, a Democrat, told us in a phone conversation this week.

When pressed, Kenney conceded -- as he did when we spoke three months ago - that they must do better.

"We have a poor population. Our poverty rate is higher than we certainly want it to be," he admitted.

That adds to the challenge every local leader is dealing with about what school will look like in the fall. Philadelphia is planning for two days a week in school and virtual learning for the other three days. The continuing issue is how to serve students who live in poverty.

"Having Internet access is really critical for them. And we're working hard with some of our companies like Comcast and others to get those key kids plugged in so that if they can't go back to school, they're at least up to speed with Internet connection," he said.

But the fundamental issue is the health care crisis in the Black community.

"The access to primary care physicians, to having your primary care physician be in an emergency room, it's been an ongoing problem, both for the residents and citizens and for the hospital emergency system itself," he said.

Kenney, a supporter of universal health care, ripped the Trump administration for making matters worse by dismantling Obamacare, never mind shirking its responsibility to, in his view, develop a national strategy to administer and pay for widespread testing.

"This is a perfect example of what federal government that's competent can do to protect the citizens of this country by having a national mask rule, by having a national testing program, by having national PPE distribution, by having all the things that we floundered on and tripped up on in March and April and May would have been resolved by a military style effort to keep all of our citizens safe," he said.

But when it comes to another flashpoint issue big city mayors like Kenney are grappling with now -- the potential for federal intervention for alleged violence -- he draws the line.

"We want federal help, but not that kind of federal help. When the administration had the opportunity to help us months ago, they refused to do so. Now he's floundering in the polls, he's playing to his base, he's playing to what he perceived to be the suburban fear of cities. And he's dividing people again, and he's making a dangerous situation, even worse, and we're prepared to fight in court in every way possible to keep that from happening in Philadelphia," Kenney said.

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Four mayors reflect on their evolving response to the coronavirus pandemic - CNN