The Washington Post’s Wonkblog carries an entry with an ominous headline, “The places in America that already have their best days behind them”. It’s about the counties across the United States that peaked in population decades ago, and it leads with Keokuk County, Iowa. Keokuk County is in red in my map above, one of 33 counties that had the most people it’s ever had in 1900. Keokuk County has issued a rebuttal via the Des Moines Register. (I agree that it’s about quality not quantity, and Iowans are the best quality you can get, but population stability would be nice, too.)
The Post article is topped off with an animated timeline map of peak population years, where you can see Iowa and northern Missouri pop out in 1900, followed by most of the rest of the Great Plains by 1940. Only a third of Iowa’s counties have peaked in 1950 or later.
The Post’s piece is based on census research from Lyman Stone, who painstakingly compiled decade-by-decade numbers for the nation. Stone’s discussion of his research includes a map of 396 counties that hit their minimum population since 1900 in the 2015 census estimates and Iowa has 46 of them, including Tama. His writeup is a good read.
(I’ve had the map made for a while; the Post gave me a hook to put it up.)