St. Mary's Help of Christians Catholic Church at Twin Sisters was the first Catholic Church in Blanco County. The first Catholic families moved here in the early 1850s. Priestly ministrations were sporadic, traceable only to 1860 when a priest visited the area and had Mass in the homes.

The land for this historic landmark was purchased in 1887 and the church completed in 1889. At a dedication ceremony in 1965 it was named a Recorded Historic Landmark, significant to the history of Texas. A weathered wooden cross atop a sturdy stone base encloses the Texas Historical Medallion and Plaque that was sponsored by Rev. Edward Rabroker and the people of St. Ferdinand's Church.

The plaque inscription reads: "In 1850s when the first Catholic families came to Blanco County worship was held in homes and halls. Land was purchased in 1887, the church was built and dedicated in 1889. Stone for the foundation came from a quarry about a mile from the site. Other materials came by wagon over thirty miles of rough roads and trails. -- Recorded Texas Historic Landmark, 1965".

In 1940, St. Ferdinand's new and larger Catholic Church was dedicated in Blanco. The church bell at Blanco is from the steeple of Saint Mary's Help of Christians Church. All services are now held in St. Ferdinand's, except that once a year in November on All Soul's Day, services are celebrated at Saint Mary's. In addition this church does serve as a chapel for the Catholic Cemetery located on these same grounds.