Individual 4-H clubs formed around the United States during the late 1800s and early 1900s to help educate young people, ages 10 to 21, about agricultural life. In 1907 or 1908, a three-leaf clover emblem was adopted nationally, standing for head, heart, and hands. In 1911, a fourth leaf was added, standing for hustle, before being changed to mean health. The 4-H system was adopted, teaching youth how to manage farms. During the 1920s, the program organized itself on state and national levels, creating requirements for clubs, projects, and leadership. In 1927, the first National 4-H club Camp was created, making 4-H a federal-state-county organization; in that same year, state 4-H leaders adopted the national 4-H pledge and motto.

In the 1930s, 4-H projects expanded from solely agricultural in focus to include home economic projects such as clothing, child care and home management as well as agricultural engineering projects such as soil conservation and tractors. During World War II, the 4-H clubs contributed to the war efforts with community service projects for collecting scrap metal and raising victory gardens, among others. The 1950s were characterized by 4-H'ers' interest in science, as well as a lowering of the age requirements to between 9 and 19 years old. For the next 50 years, 4-H continued to grow and contribute to society by offering a learning experience for youth, as well as a social outlet. The national organization celebrated its centennial in 2002.

The first 4-H county camp in Virginia was held in Loudoun County in 1917 for tomato and canning clubs. The first Loudoun County 4-H Fair was in 1936 at the Fireman's Field in Purcellville. The annual fair was held in that spot until 1954, when it moved to the Middleburg Community Center. Two years later, the Fair moved again to Lincoln Elementary School. In 1956, Clarence R. Ahalt (1888-1962) and his wife Tillie A. Ahalt (1889-1979) donated 13 acres of land to the Loudoun 4-H organization. Since 1957, the Fair has been held on those 13 acres, located just west of Leesburg. In 1993, a 4-H scholarship program was set up by the Loudoun 4-H Clubs & Associates. The 70th anniversary of the County Fair was celebrated in 2005.