CHEYENNE, Wyo. (AP) — In recent years, more visitors to Yellowstone National Park are being cited for possessing small amounts of medical and recreational pot. Rangers say many visitors from states where medical pot in particular is legal don't realize it's still off-limits on federal land.

The U.S. attorney's office in Cheyenne says it prosecuted 21 marijuana cases from Yellowstone in 2010. That number rose to 52 in 2013 and, as of mid-December, 80 cases in 2014.

Those convicted of misdemeanor possession commonly receive a $1,000 fine. The numbers are small compared with the nearly 4 million visitors who trek each year to Yellowstone, the nation's first national park.