Travel Shot: St. Mary Lake, Glacier National Park, Montana CheapOair Staff August 13, 2010 general Glacier National Park is free to visit this weekend St. Mary Lake is the second largest lake in Glacier National Park, Montana. The scenic lake is 9.9 miles in length and three hundred feet deep. Used mostly for trout fishing, the lake barely rises above a chilly 50 degrees in temperature. During the winter the lake is frozen solid with four feet of ice. This weekend you can visit Glacier National Park, or the nearly 400 other U.S. National Parks, for absolutely free. That’s because admission has been waived Saturday August 14 and Sunday August 15 by the National Park Tourism Services to help promote some of the nation’s most beautiful and affordable places to visit. Commenting on the fee-free weekend, Salazar said in a statement, “I encourage everyone to take advantage of the free admission to visit not only our greatest natural wonders but also our nation’s historic and cultural icons.” Source: nps.gov