St. Thomas Church was organized in 1834 by the Reverend Samuel George Litton.  Mr. Litton was a native of Ireland and a graduate of the University of Dublin.  Bishop Otey, the first Bishop of Tennessee, sent the Reverend Litton into this newly settled area of the state known at that time as the Western District.  The present building was erected in 1858.

From May 14th through 19th of 1861, the thirty-third annual convention of the Episcopal Diocese of Tennessee was held in this church, and the building was dedicated at that time.  Fort Sumter had surrendered a month before, and Tennessee was to secede a few weeks later.  The confusion and perplexity of the times is reflected in the discussion at the convention of whether the prayer for the President of the United States should be retained in the prayer book.  It was left to the discretion of the individual ministers.

The window over the altar of the church was given in memory of the Right Reverend Davis Sessums, Bishop of Louisiana, by his family, some of whom formerly lived in Somerville.  The first window in the west wall is a memorial to the Reverend John Miller Schwrar, the Rector in 1878 who was advised to leave but remained at his post and died of yellow fever during the great epidemic of that year.  The marble cross on the altar is a memorial to his wife, Anna.  The other memorial window was given by the family of John Cowan Humphreys, Circuit Court Judge before the Civil War.  The baptismal font is a memorial to Mary Lewis Scott.  The altar, made of local cherry, is a memorial to Mrs. Jane T. Williams.  Communion vessels were made from silver given by the members of the Ladies Guild in the 1890's.  The brass lectern was erected in memory of Colonel Thomas S. Galloway, and the processional cross is a memorial to the Cocke and Juny families.  Three Reverend Messrs. Juny have served here, and Miss Margaret Juny was organist and choir director for many years.