In 1971, before the George Parks Highway connected McKinley National Park to Fairbanks [1] (125 miles) and Anchorage [2] (245 miles), you had to take the train, or from Fairbanks you had to drive down to Delta Junction, take the Richardson Highway to Paxson, the Denali Highway [3] to Cantwell, then the Parks Highway up to the park entrance, for a grand total of 340 miles.
From Anchorage you had to drive to Glennallen [4], then up the Richardson to Paxson, over to Cantwell and beyond, for 440 miles. That year, nearly 45,000 visitors passed through the park.
In 1972, when the George Parks Highway radically reduced driving times from both main urban centers, almost 90,000 visitors came. In anticipation of the huge jump in tourism, the Park Service initiated the shuttle system of school buses [5] running a regularly scheduled service along the Park Road. Today, Denali National Park [6] sees 400,000 visitors annually.
Links:
[1] http://www.moon.com/destinations/alaska/the-interior/fairbanks
[2] http://www.moon.com/destinations/alaska/anchorage
[3] http://www.moon.com/destinations/alaska/the-interior/talkeetna/sights/denali-highway
[4] http://www.moon.com/destinations/alaska/the-wrangells-and-prince-william-sound/copper-river-valley/glennallen
[5] http://www.moon.com/destinations/alaska/the-interior/denali-national-park/getting-around-denali/denali-shuttle-bus-tours
[6] http://www.moon.com/destinations/alaska/the-interior/denali-national-park