Carley Calvi came to the second floor of a public library in suburban Milwaukee one morning this month without health insurance to cover the vertigo medication she needed. Worse, she said, was not having a doctor she trusted.

“I want somebody to value me as the person I am,” said Ms. Calvi, a 35-year-old woodworker.

With roughly 110 options and the help of a health insurance navigator, she selected a plan with a steeply discounted $221 monthly premium, placing her among the 21.3 million people who have signed up for coverage on the Affordable Care Act’s marketplaces for 2024. The sign-up total, announced by the Biden administration on Wednesday, set a record for the third year in a row and amounted to almost double the number of sign-ups from 2020.

Driving the surge in enrollment has been the continuation of more generous federal subsidies that date to the coronavirus pandemic.

President Biden and Democrats in Congress expanded the subsidies for two years as part of a pandemic relief package in 2021, and they later enacted a three-year extension that runs through 2025, meaning that Americans will be able to take advantage of the beefed-up assistance for one more annual open enrollment period.