The Watts Towers are a National Historic Landmark consisting of 17 interconnected structures built by one artist, Simon Rodia, between 1921 and 1955. As part of an ongoing effort led by the Los Angeles County Museum of Art to preserve the Towers, UCLA engineers have been experimentally and analytically studying how environmental factors affect the structural behavior and crack movements. Measured thermal effects on the tower include shifts in the structure's fundamental frequencies, daily tilting patterns, and daily crack movement. A finite element model was created in order to further study the observed thermal effects. Modeled thermal tilt behavior was consistent with measured results, but the magnitude of tilt was 80-90% lower than measured. Earthquakes and windstorms have previously caused damage to the Towers. The current data set shows that both small earthquakes and moderate winds produce motions exceeding thermal levels. Monitoring will continue to capture larger earthquakes and windstorms.