They Had an Answer to Their City’s Decline. Then Came the Immigration Crackdown.

Shrinking cities have tried to stabilize their populations with foreign-born residents. The strategy was working, until the inauguration.

At a high-traffic intersection on the south side of St. Louis, in a former bank building complete with a glassy atrium, it’s time for sewing class — held in Dari, the Afghan variant of Persian.

The walls are hung with photos of Afghanistan, from which most of the students have recently arrived. Before class starts, a handful of women in sneakers and head scarves first go to another room for prayer, while their younger children scamper around a well-equipped play room. They return to dated sewing machines, learning how to run tiny businesses from their homes as they acclimate to their new country.

The two-year-old Afghan Community Center has been an anchor for Halima Osmani, 20, who arrived from Afghanistan last summer with her parents and seven siblings. She now runs her own tailoring business, selling to local women through an Instagram account, while she works on getting her G.E.D. Eventually, she wants to become a physician assistant, and St. Louis seems like a good place to fulfill her dreams.

“Our first choice was Virginia, but we ended up here and liked it,” Ms. Osmani said through a translator; she is still learning English. “The first thing we noticed here was that it wasn’t crowded.”

Not being crowded — that’s both a problem and an opportunity for the grand but diminished city, which has been losing population for decades. The city’s politicians, business community, religious institutions and philanthropists have embraced a push to reverse that trend through immigration. In addition to refugees like Ms. Osmani, they’re trying to attract people from Central and South America, as well as international students and highly skilled professionals on employment visas.