SR 99 starts in Leupp on the Navajo Nation and heads south to Interstate 40 west of Winslow.

From there, the route runs concurrently with I-40, then exiting I-40 in Winslow onto Business Spur 40.

The route heads towards the edge of the Apache Forest, where state maintenance ends.

[2][3] A designation of the nearby State Route 377 was deleted in 1983 and added to SR 99.

Media related to Arizona State Route 99 at Wikimedia Commons