Visitation to some of the most popular national parks in the United States has surged in recent years, but in many national park units, attendance has declined even as the U.S. population increases. Changing demographics, patterns of visitation, maintenance needs, and inconsistent federal support raise questions about national parks' relevance to younger generations. In particular, the attitudes of the U.S. Millennial generation are a key concern for park managers and supporters. We evaluate the views of a sample of Millennials toward America's national parks and find that many lack basic knowledge about national parks, yet still say they value and appreciate the national park system. Land managers should respond to knowledge gaps of Millennials and pursue outreach that strategically consolidates the support of this and younger generations for a national parks system that is expected to provide ecological and cultural benefits for current and future generations.