Another possible reason: There are more financial resources for low-income women to pay for abortion. Ms. Jones noted that an uptick in charities that offer financial help has made it possible for more women to afford an abortion. Also, Medicaid expanded in several states under the Affordable Care Act, increasing coverage for poor women, and in turn, coverage of abortion in states that allow their Medicaid programs to pay for it.

At Hope Clinic for Women, in Granite City, Ill., just across the Mississippi River from Missouri and a quick drive from downtown St. Louis, more than half of all patients require some financial help. Many call the National Abortion Federation Hotline Fund, a national nonprofit that gives out small grants, often of a few hundred dollars, to help women pay for abortions and sometimes for travel. They also get help from the Gateway Women’s Access Fund, a local charity set up in 2015 to help Missouri patients.

That is what helped a young woman from St. Louis, who arrived at the clinic for an appointment last Friday. She had with her $560, part of which she had saved from her job answering phones on a hospital switchboard. But when she was told she needed another hundred dollars because of her blood type, she began rapidly texting, hoping she could borrow it. She even called her mother, something she said she didn’t want to do.

“I’m short $100, can you lend it to us?” she asked her mother, in a quiet voice.

The crisis passed when a clinic worker, Cali Baublitz, said she could cover it using money from the Gateway fund.

As the number of abortions has declined, the map of abortion access across the country has become uneven, with red states passing ever-stricter laws and blue states moving in the opposite direction.

Missouri is now one of six states with only one clinic left. The others are Kentucky, Mississippi, North Dakota, South Dakota and West Virginia. That has created surges in adjacent states, and at border clinics like Hope, whose patient load was up by 35 percent this June, compared with the same month a year ago, according to Dr. Erin King, the clinic’s executive director.