This is a limber pine tree that was seeded and grew in the crack of an ancient granite boulder, some distance from any similar tree. It was present when the railroad came by in the 1860s.
The description states:
Lone Tree. This Tree, growing out of solid granite is 76 years old. This tree is located on the Lincoln Highway 28 miles west of Cheyenne.
–More commonly called Tree Rock, the monument, little changed in many decades, is now in the median strip of Interstate 80 where vehicles passing by can pull off in the center of the highway to examine the site.
This card likely dates from the 1940s.