In 1910, an opera house with a "small amount of scenery" occupied the second floor of a building at about 130 South Broadway.  The first floor was split between a drug and furniture stores.
Sanborn Fire Insurance Map, 1910
Broadway Opera House

130 South Broadway
Green River, Utah 84525

The Broadway Opera House was open from about 1914 to 19201  Sanborn fire insurance maps from 1910 and 1917 show an opera house occupying the second floor of a building about 130 South Broadway.

1. Polk's Utah Gazetteer and Business Directory, 1914-1915, 1918-1919, 1920-1921