On January 22, 1862, a territorial post office was established at Huntsville, Douglas County, Colorado. It was discontinued on August 29, 1867 and reestablished on April 8, 1869, and the name was changed December 13, 1871, to Larkspur. The Larkspur post office has been continuously in operation since that date. In 1871, the name Huntsville was changed to Larkspur by Elizabeth Hunt who was the wife of then Governor and she named the town after the flower that grows so profusely in the area.

     The Denver and Rio Grande Railway in its construction south from Denver reached Larkspur on September 21, 1871. On September 24, 1871 the railroad reached "Pineland" a station about 4 miles south of Larkspur. There was no Pineland post office established. Subsequently, the name was changed to Greenland, and the Greenland post office was established June 3, 1873. The Greenland post office was discontinued March 31, 1959 and it was replaced by a rural route from Larkspur.

     A one room wood schoolhouse was built on a ranch south of town in 1872. It was later put on skids and moved into town. Folklore has it that the original wood schoolhouse was destroyed by a tornado, but no documentation can be found to substantiate that story. However, in May of 1896 a new brick schoolhouse, which still stands today, was built. Historical records show that the schoolhouse was used for church services, social activities and community meetings.

     In the 1920's, Larkspur had a reputation as a health and summer resort. At that time, Larkspur had one hotel, a lumber camp adjoining the town, a general mercantile store, blacksmith shop, orphanage, hardware store, grocery store, and the Frink Creamery Company, founded there in about 1900 and known for their popular Black Canyon Cheese. Most of the buildings and businesses along Main Street near Plum Creek were destroyed in the large flood of 1965. The main street of town then moved higher up on the hill to Spruce Mountain Road in front of the old school. In 1972, a large new school was built on Perry Park Road and the old schoolhouse was sold to a private party.

     One pioneer settler in the area was Jimmy Riggs, who moved to Douglas County in 1881 and opened his store at Greenland. In 1923 he moved his store to Larkspur. He served as County Treasurer for two terms. He passed away at the age of 80 in 1938.

     The town was incorporated as a home rule municipality on May 21, 1979. Anne Trueblood was the town's first mayor. Since that time the town limits have grown as a result of poverty annexations.