BILLINGS, Mont. -

 Montana parks are celebrating their 75th anniversary this year.

The anniversary commemorates the state's first park, Lewis and Clark Caverns.
    
Montana has 56 state parks, 54 of which are operating fully. All are free to Montana residents. A $6 fee charged when you license your vehicle provides the major funding for operation of the parks. Out-of-state visitors pay a $5 fee per car to enter state parks.
    
In 2013, there were 2.1 million visits to Montana state parks, which broke the previous record. Those visitors spent $289 million within a 50-mile radius of the state parks.
    
Jennifer Lawson is marketing director for Montana State Parks.
    
Lawson tells The Billings Gazette  that state parks are an economic engine for Montana.