In 1761, a mission church, then called Saint George's, was established on a plot of ground on East Main Street, just south of the Northern Westchester Hospital complex.
St. Mark's was formally recognized as a religious corporation in New Castle in 1850, largely through the efforts of the Reverend R. M. Harris, rector of Grace Church, White Plains.
A new church was built on the site of the earlier Saint George's which was sold in 1819 due to extensive damage from Revolutionary War battles. According to records, the new building was a "model for a country church, 50 by 30 feet with a tower projecting 8 feet in front." Exclusive of stained glass and the furniture, it cost $2,050. The burying ground, which was in back of Saint George's and then St. Mark's, remains to this day. It contains graves dating back to the Revolutionary War.
With the coming of the railroad, the community around the Mount Kisco station began to grow. In order to serve the new people, it became necessary in the early 1880's to hold missionary services at the Town Hall. In time, it was felt that the church should be nearer to the new community, so the Rector, the Reverend Egisto F. Chauncey, bought a lot for $420, upon which the present church stands. In 1910 Mr. Chauncey engaged the firm of Cram, Goodhue and Ferguson to build a new church. Mr. Bertram G. Goodhue undertook the work, the cost to be $60,000.
The cornerstone was laid in 1910, and is inscribed with these words in Latin: "St. Mark's Church, Mt. Kisco, N.Y., 1910. ‘Where there is no vision the people perish'" (Proverbs 29:18). On St. Mark's Day, 1917, the new church was consecrated by the Right Reverend David Hummel Greer, Bishop of New York. In 1921 the Peace Tower was dedicated, and in 1929 the south aisle and the Parish House were added. In 1954 the Parish House was remodeled to provide classrooms for a growing Church School. The most recent addition was the Columbarium which was added to the south of the Church, in 1961.