The Holly Theater, Medford, OR. It opened in 1930. After a period of deterioration and disuse, the exterior was recently restored to its former glory, with an official lighting ceremony in April of 2012.
The Fallon Theater, Fallon, NV. Opened in 1920 as the Rex. The Fallon is the longest continually operating movie theater in Nevada.
The Regal Tigard 11 Cinema in Tigard, Oregon. I think it opened in the 1990's, but I haven't found anything to verify this.