The introduction of Marketplaces under the Affordable Care Act greatly expanded individual-market health insurance coverage in 2014, but millions of adults continued to purchase individual coverage outside of the Marketplaces. Using data from the National Health Interview Survey, we found that the number of adults ages 19–64 covered by individual-market insurance nearly doubled after the ACA’s implementation. In 2015, there were 8.6 million nonelderly adults enrolled in Marketplace plans and 6.3 million off-Marketplace purchasers. Compared to Marketplace enrollees, off-Marketplace enrollees were more likely to be male, be white, have higher incomes, and be in excellent or very good health.