Grand Canyon Railway: huge spike in business in 1916?

The ICC annual reports (1914, 1916, 1917) show operating revenues (in thousands) for the Grand Canyon Railway as 264 in 1914, 1002 in 1916, and 307 in 1917, with the increase mainly in passenger revenues (passenger counts in thousands were 49, 181, and 54). By the way, this made the ICC classify the Grand Canyon Railway as Class I in 1916. Does anyone know why there was such a large spike then? It doesn't seem to coincide with any major events at the park; could there have been a bunch of advertising by the Santa Fe at about that time?

I'm uncertain about the events in the park itself but that is the year that the National Park Service itself is created.

Sounds plausible, but the 1916 report is actually for the year ending June 30, 1916, and the NPS was created August 25. It also apparently didn't take control of the Grand Canyon until 1919, so it's probably not from some sort of preparatory activities.