President-elect Trump has consistently vowed to repeal the Affordable Care Act, and promises to take action on day one of his presidency. With Republicans holding a majority in both the U.S. Senate and House of Representatives, action against the health law seems imminent in 2017.

Today over 20 million people have health insurance because of the ACA, including more than 6 million young adults now permitted to stay on their parents’ plans until age 26.

While a number of states established their own exchanges, thirty-seven states opted to use the federal health marketplace rather than administer their own exchanges. As of early 2016, there are over 8 million people across the United States enrolled through These 8 million people would be most immediately affected by a repeal.

Map of Participants in Federal Health Marketplace by Zip Code

Note: This figure shows thirty-seven states without state-based marketplaces. It excludes zip codes with fifty or fewer individual enrollees.

Source: U.S. Department of Health & Human Services

Cover photo: LaDawna Howard, King vs Burwell – Rally in support of Obamacare – US Supreme Court, June 25, 2015.