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

Broadway Opera House

130 South Broadway
Green River, Utah, 84525
(1908 - 1920)

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