Thankful Memorial Episcopal Church and St. Elmo are indebted for their existence to Colonel Abraham Malone Johnson. Born in Gainesville, Georgia in 1830, he came to Chattanooga in 1851 where he went into the tanning business with his brother-in-law, John P. Bryson. Two years later, he was given a position as a post office route agent on the Nashville and Chattanooga Railroad line. During this time, he met Thankful Anderson Whiteside, the daughter of one of the founders and leading citizens of early Chattanooga, Col. James Whiteside.

Col. Whiteside came to the area in 1838, the year the Indians were removed and the Cherokee lands were put up for sale and the year Ross’s Landing became Chattanooga. He was an early developer of Lookout Mountain and was instrumental in making Chattanooga a thriving railroad center in the pre-war South. His daughter, Thankful Whiteside, was named after her grandmother, Thankful Anderson, who in turn was named for Thankful Doak, a baby born at sea during a terrible storm, hence the name. Col. Whiteside endorsed and promoted his daughter’s impending marriage to a young man from Shelbyville who had come to Chattanooga to study law. Col. Whiteside’s plans were thwarted, however, when Thankful eloped with Col. Johnson two days before the planned wedding to the law clerk in 1857. It wasn’t until the birth of twins a year later that Thankful was reconciled with her father. Ironically, Col. Johnson’s own daughter, Annie, eloped with Jack Betts two days before her own wedding. The headlines in the Chattanooga News read: "On Her Wedding Day Pretty Annie Johnson Prefers Another".

Soon after his marriage, Col. Johnson became superintendent of the new Will Valley Railroad. During the Civil War, he operated several railroads in Georgia, serving under the Confederate government with the rank of colonel. As a Confederate railroad operator he kept his family (and others) safe by filling boxcars with their worldly possessions and moving them around the South to avoid the conflict.

When the war was over, the Johnson’s returned to Chattanooga to find their home and belongings destroyed. Col. Johnson became president of Lookout Savings and with three others bought the Lookout Water Works, which was built by Union soldiers. He spent the next seventeen years supervising the construction of the Chattanooga water system.

An outbreak of yellow fever in 1878 caused a panic that sent Chattanooga residents fleeing to the hills and mountains to avoid the disease. Seeing this demand for mountain homes and property, Col. Johnson began subdividing lots on the farmland his wife had inherited from her parents on the eastern slope on the foot of Lookout Mountain. He then hand-picked the citizens who bought the land plots. Overlooking the community, the Johnson’s built their home, known as "The House", located on two city blocks. He named the community St. Elmo after a novel of that name by Augusta Evans. Evans, a personal friend of Col. Johnson’s wife, said the view of the new community from Lookout Mountain reminded her of the view of St. Elmo castle in Naples.

St. Elmo had two advantages over the other new suburbs being developed: Johnson installed a water main to provide city water and there was an electric trolley car that connected St. Elmo with Chattanooga by 1887. The Episcopalians who lived in St. Elmo attended St. Paul’s Church, but it was a long, slow journey even with the available trolley. Thankful Everett, granddaughter of Thankful Johnson recalled, "…in the 1890’s, the street car and the family horse and carriage were the only means of transportation from the village of St. Elmo… into Chattanooga and the mother parish of St. Paul’s. So attending church was not a simple matter… it took time to make the trip."

Thankful Everett asked the rector of St. Paul’s for permission to start a children’s Sunday School in St. Elmo because many mothers feared their children were not being properly exposed to the practices and beliefs of the Episcopal Church. A preliminary meeting at the Johnson house in 1892 led to the first meeting of The Guild of St. Elmo Sunday School on October 29, 1893 in the brick music hall at the corner of St. Elmo Avenue and 45th Street (the current location of St. Elmo Avenue Baptist Church). The Guild rented the space from the St. Elmo Social Club for the rent of $3.00 per month. W.H. Wilson served as the first superintendent while Col. Johnson served as the first secretary. By 1895, eighteen women taught Sunday classes there. Members of the Guild and their husbands financially supported the school until it became a mission in 1898 when the Rt. Rev. Thomas F. Gailor sent Rev. William G. Robertson from Sewanee to conduct services. In 1899, Mr. Francis Lynde, who had given up his profession as a railroad engineer to become a successful historical novelist, became the first lay reader of the Episcopal Mission and conducted services along with Rev. Goodman from St. Paul’s Church. Under their direction, the Mission became a "semi dependent congregation…entirely self-supporting".

When Col. Johnson died in 1903, he bequeathed property across the street from his home to be used for an Episcopal Church to be named in memory of his wife, Thankful Anderson Whiteside Johnson. Hence in 1904, the Episcopal Mission ended with the construction of Thankful Memorial Episcopal Church, a church built of native stone in Gothic revival style and filled with several stained glass windows from the Johnson home. A stone that had supported the "Old St. Paul’s" brick church on Chestnut Street that was saved in the Johnson garden became the cornerstone for the new building. The bell still in use for Sunday services was loaned in perpetuity by St. Paul’s when their new chimes were installed in 1911.