It could take up to five days for a tourist on muleback to reach Havasu Canyon in 1947. But take one look at the brilliant blue-green water of Havasu Falls, and it's obvious why so many have decided to make that particular Grand Canyon excursion. As LIFE put it back then, "A tourist usually visits the Grand Canyon only long enough to realize how much more he could see and learn if he stayed longer."
That image was one of the few photographs printed in color for a story LIFE ran that September about the Grand Canyon and its geology, history and wildlife—and, last but not least, its appeal to tourists. The couple of color images that made it into the magazine, however, represented just a slice of what LIFE kept to itself or printed in black and white; a few of those unprinted images can be seen here. Grand Canyon National Park was established in 1919, and by the time that article was published, about a half a million visitors made their way there each year. Today, that annual count is ten times higher, with a whopping 5 million tourists exploring one of America's greatest natural wonders. As National Park Week kicks off on Saturday, with its offer of free park admission, the 2016 tally is sure to be on its way up there once again.
Liz Ronk, who edited this gallery, is the Photo Editor for LIFE.com. Follow her on Twitter @lizabethronk.