UNDATED -- The Minnesota Department of Natural Resources says sales of state park permits went up by 2% in 2013. A total of 136,300 permits were sold last year.

The number is also up 21% since 2008.

A DNR spokesman says the increase in popularity may be a general trend toward more families "stay-cationing" to save money, and programs and special events designed to attract visitors.

Participation in interpretive programs has increased by 37% since 2008 when voters approved the Clean Water, Land and Legacy Amendment. It's tax money set aside to help fund park improvements and programs.