This dissertation examines the health insurance status of young adults during the transition to adulthood. In a series of three essays, I analyze what happens as young adults reach important milestones and the effects of public policies. The first essay is a descriptive study on how insurance status changes after reaching age 19 and graduating from college. The likelihood of becoming uninsured rises sharply once turning age 19 and then peaks at age 23. While the proportion uninsured also increases following college graduation, this increase disappears after one year. The second essay analyzes the effect of a dependent age law in New Jersey, which allowed dependent coverage for young adults up to age 30 and did not require full-time student status. Pennsylvania did not pass a law and was used as a control state. Among 19-to-22-year olds, there was a rise in health insurance coverage in New Jersey relative to Pennsylvania. There also was a negative effect on college enrollment in New Jersey relative to Pennsylvania. The final essay considers other unintended consequences of dependent age laws. Using a national dataset, I estimate that there were no clear effects on decisions related to living arrangements, marriage, and full-time employment.