Bierstadt was from the school of painting known as Luminism, which preceded the Tonalists.

George Inness is a well known Tonalist. This is his Sunrise in the Woods - 1887:

I've been a fan of Tonalism for some time, but only recently developed an appreciation for the surreal nature of Luminism. Tonalism has a touch of the surreal, but tends towards dreamlike simplification. Luminism is high fantasy.

Bierstadt's Among the Sierra Nevada, California -1868

I've always felt like it was just a bit too much. But, I imagine that was the point.