18th century The property was originally part of the Northampton land grant given to Col. Henry Darnall (c. 1645–1711), a relative of
Lord Baltimore, in 1695. , Hampton's second master By the late 1750s, Hampton extended to more than and included an
ironworks. In 1783, Capt. Ridgely began construction of the main house, Hampton Mansion. He said its concept was inspired by
Castle Howard in England, owned by relatives of his mother. When Capt. Ridgely died that same year, his nephew,
Charles Carnan Ridgely (1760–1829), became the second master of Hampton. Prominent artisans of the time were hired to design geometric formal gardens, which were planted on the Mansion's grounds between 1799 and 1801.
19th century Under Charles Carnan Ridgely, Hampton reached its peak of in the 1820s. The vast farm produced corn, beef cattle, dairy products, hogs, and horses. Charles Carnan Ridgely frequently entertained prominent guests in the Mansion's 51 ft. x 21 ft. (16 m by 6.4 m) Great Hall, such as
Charles Carroll of Carrollton, who was a signer of the
Declaration of Independence, and Revolutionary War general, the
Marquis de Lafayette. By the mid-19th century, the Hampton estate had one of the most extensive collections of citrus trees in the U.S., along with various exotic trees and plants gathered by Eliza Ridgely during her frequent travels to Europe and the Orient. In January 1861, shortly after the election of
Abraham Lincoln as
President of the United States, Charles Ridgely (the son of John Carnan and Eliza Ridgely) formed the pro-
Confederate Baltimore County Horse Guards at Hampton with himself as captain of the militia unit that he described as "
states' rights gentlemen." One of his militia's cavalry men,
Lieut. John Merryman, was subsequently arrested by the
Union Army and imprisoned in May 1861 on a charge of
treason, sparking the landmark
U.S. Supreme Court case,
Ex parte Merryman. As the
Civil War raged across the farmlands of Maryland and Pennsylvania at the
Battle of Antietam (1862) and the
Battle of Gettysburg (1863), the Ridgelys' Hampton estate remained untouched. The Hampton Mansion remained in the Ridgely family until 1948, when John Ridgely Jr. moved to the smaller Farm House on the property and the Mansion was acquired by the Avalon Foundation (now part of the
Andrew W. Mellon Foundation). The seventh and last generation of Ridgelys to live at the mansion was his son, John Ridgely III , who, after marrying Lillian Ketchum in the mid-1930s, continued to reside at the mansion with his wife until they both entered Army service during World War II. The Hampton Mansion and remaining of the Ridgely estate were designated a
National Historic Site by the
Secretary of the Interior on June 22, 1948—the first site to be so selected on the basis of its historical significance and "outstanding merit as an architectural monument". Hampton Mansion was opened to the public in May 1949 under the care of Preservation Maryland for the next thirty years (1949–79). Work also began in 1949 to restore four of the site's six 19th-century parterres. On October 15, 1966, Hampton was listed on the
National Register of Historic Places. In October 1979, it was acquired by the
National Park Service (NPS), which has operated and managed the estate since. The NPS subsequently acquired additional acreage containing original Ridgely structures, bringing the park to its present size. Critical needs were identified, such as the lack of a fire suppression system and climate control. Conservators of the property's furnishings and paintings said that the need to stabilize temperature and humidity levels inside the mansion was "urgent due to unacceptable environmental stress". Starting in January 2005, the mansion closed for almost three years as it underwent the major restoration project. As part of the 2005–07 renovations, the drawing room and two bedchambers were completely refurbished. The drawing room's furnishings were extensively researched to reflect accurately the Mansion in the 1830–60 period. The ornate
cupola atop the mansion was restored, including the spherical ornament above the cupola, which was refinished in
gold leaf. The Hampton Mansion re-opened to the public on November 30, 2007. As of 12 November 2025, visitors can still read ″Stories of the Enslaved″ and ″Free Black Laborers″ on the park′s website. ==National Park Service management==