From the record
“The Franklin County Courthouse and Jail in Mount Vernon, Texas was built in 1912. It was listed on the National Register of Historic Places in 2006.”
Wikipedia article Franklin County Courthouse and Jail, CC BY-SA 4.0.
One of 4 National Register listings published here for Franklin County · listed in 2006 · category: Building.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service