Theon is on Farm Road 1105 thirty-one miles north of Austin in north central Williamson County. It was settled after 1880 by German and Slavic immigrants and at one time had a post office, a church, a general store, a saloon, a cotton gin, a corn mill, and a gas station. The Holy Trinity Catholic Church was established in 1889 and was still active in 1990. The church was built in 1913, and the Moravia Hall dates from 1938. The community no longer has a post office; the school was merged with the Jarrell school in 1948. The estimated population in Theon was twenty from 1950 through 2000. The Possum Inn, a tavern and cafe, is the only business in town. In 1984 this establishment was noted for displaying a large glass bowl of live rattlesnakes on its bar.