(Felicia Fonseca | The Associated Press) In this Aug. 19, 2015, file photo, visitors gather at an outlook on the South Rim of Grand Canyon National Park in northern Arizona. National parks in the U.S. will sharply drop the number of days it allows visitors to get in for free. After waiving entrance fees for 16 days in 2016 and 10 days in 2017, the National Park Service announced Tuesday, Dec. 12, 2017, that it will have four no-cost days next year.