Federal officials say national wildlife refuges offer benefits to humans as well as wildlife.
According to a U.S. Fish and Wildlife Service report released last week, refuges pump $2.4 billion into the economy and support more than 35,000 jobs.
That money comes from the 46.5 million people who visited national wildlife refuges in the 2011 fiscal year.
Florida tops the list of the most visited parks, with six national refuges racking up more than 3 million visitors. Merritt Island National Wildlife Refuge near the Kennedy Space Center is the most popular, attracting 1.2 million visitors.
Other Florida refuges are known for attracting large numbers of manatees and nesting sea turtles, as well as human visitors.
U.S. Secretary of the Interior Sally Jewell says visitors to the country's network of national wildlife refuges support restaurants, hotels and other local businesses.