Pinellas County (St. Pete) probably has the most unique population history of anywhere.
1940 91,852 47.8%
1950 159,249 73.4%
1960 374,665 135.3%.....yes, it doubled + a third
1970 522,329 39.4%
1980 728,531 39.5%
1990 851,659 16.9%
2000 921,482 8.2%
2010 916,482 -0.5%
2020 978,872 9.4%
If you're unfamiliar, "What happened?" you might ask.
It's full. There's nowhere for it to grow. There's a bay and an ocean and a border. I'm guessing the recent 9% growth is strictly vertical, in taller buildings. There's literally no more landmass to grown into.