The Leesburg Garden Club was founded 9 December 1915 by four women, Mrs. Page (Bessie H.M.) Laughlin (1876-1950), Mrs. John (Frances P.) Gibson(1882-1964), Mrs. J.R.H. (Cora L.) Alexander (1884-1972), and Mrs. William (Norita F.) Martin (1876-1952). Early in 1916 eight additional women were invited to join, and by the end of 1917 there was a total of 22 members. By 2010 membership was limited to 40 active members, 10 associate members (members who for reasons acceptable to the Executive Board can no longer be active but who are entitled to the privileges of the club including voting), one non-resident member and such honorary members as the club and the Executive Board vote to include. Honorary members are people who have benefitted the club to a considerable extent. For example, the husband of a member was made an honorary member because of his work growing and hybridizing lilies which the club entered in many shows and with which it won many ribbons.

The club began as a group who met to read aloud from the works of Charles Dickens (1812-1870). One member mentioned hearing of something called a "garden club" and so Dickens was abandoned in favor of plants. Although named the Leesburg Garden Club, members came from all sections of Loudoun County and in the beginning many of them lived on farms as well as in the Town of Leesburg. Almost all had vegetable gardens, so there was initially as much emphasis on vegetables as on flowers.

On 18 May, 1926 the Leesburg Garden Club became the 14th member of the Garden Club of Virginia (GCV) which had been founded in 1920 with the object of encouraging preservation, conservation, beautification, and restoration in the state. The GCV organized Garden Week in Virginia to earn money for this purpose and in 1929 the Leesburg Garden Club opened two historic houses and made "about $16." Proceeds have increased tremendously and by 2010 the club's gross receipts surpassed $10,000 for Garden Week, which takes place at the end of April each year.

From the beginning the club had a number of civic projects as well as the members' own interests in gardening. Starting in 1917 members supplied fresh vegetables to the local hospital from their own gardens and from a garden which they established on the hospital grounds. They canned produce to provide vegetables for the staff and patients in winter in the days before freezers. This program continued until the early 1940s when the club switched its attention to landscaping at the hospital. Members also planted flowers to cheer up patients. Another early project was to help elementary school children plant flowers and teach them about beautification. This project expanded to become the Highway Development Committee and eventually the Beautification Committee which promotes the aesthetic improvement of Loudoun County and its towns and highways.

The club's concern with county beautification led it to work actively in opposition to the use of billboards. One member, Vinton Liddell Pickens (1900-1993), particularly urged the use of zoning to prevent the construction of billboards. She regularly attended meetings of the Board of Supervisors until the board agreed to appoint a Planning Commission to write a zoning ordinance. Vinton Pickens was the commission's first and longest serving chairman. Through the work of the Leesburg Garden Club, in 1942 Loudoun County became the first rural county in the country to have a zoning ordinance.

In 1985 the club became embroiled in a conflict with Lyndon LaRouche (1922 - ), an extremist political figure. LaRouche moved his headquarters to Loudoun County, and one of his organizations, Campaign Publications, Inc., filed for a variance to change the use of its agriculturally zoned property. The Leesburg Garden Club joined other concerned groups and citizens to protest the request. The Board of Zoning Appeals denied the request in February of 1986, and LaRouche and his supporters targeted those who opposed the variance with media attacks. Leesburg Garden Club members were described by LaRouche in an interview as "these clacking busybodies in this Soviet jellyfish front sitting here in Leesburg oozing out their funny little propaganda making nuisances of themselves."

The Leesburg Garden Club became a non-profit 501c3 organization in 1999 and has continued its civic work in order to maintain that status. The club has worked with Oatlands Plantation and Dodona Manor in preserving and maintaining these historic properties, which are open to the public. Each year it sends a child to Nature Camp where he or she learns the value and interest of nature conservation. A college scholarship is awarded each year to a high school student who will be studying in a horticulture related field. A long established custom has been for the members to meet in December to create wreaths and decorative greens to hang on Leesburg's unique swinging courthouse yard gates and the doors of Thomas Balch Library, the town's history and genealogy library. Other projects undertaken in the past have included encouraging homeowners to beautify their yards by giving them daffodil bulbs, planting dogwood trees in public spaces, and persuading the town of Leesburg to place hanging baskets of flowers on utility poles. The club monitors the county's sign ordinance and works with the county when amendments are necessary; this has happened only twice in the 70 years since it was adopted as part of the zoning ordinance.

The club also is active in gardening activities such as horticulture, flower arranging and flower shows. It takes part in the major GCV shows as well as sponsoring them when its turn comes in the GCV rotation. Members have won statewide awards for their work in conservation, preservation and beautification including, the GCV Massie Medal four times for saving the Broad Run bridge, introducing zoning to the county, for horticultural achievement and for donating trees for the Douglass Community Center "Park for all Ages." The club won the GCV Common Wealth Award for that park, and a member won the GCV deLacy Grey Memorial Medal for her work to protect the natural resources of the commonwealth. 10 members have won the GCV Horticultural Award of Merit.