The land had been part of an estate called Auchentorlie, owned by Dr. George Buchanan, one of the seven commissioners who established Baltimore Town in 1729. Buchanan's country estate northwest of the colonial town included 579 of the 745 acres that make up the park today. Colonel Nicholas Rogers, who married Buchanan's descendant Eleanor, renamed the place Druid Hill. In 1860, Baltimore mayor Thomas Swann pushed through a one-cent tax on horsecar fares to raise money to purchase the land for a public park. The city bought it from Lloyd Rogers and Swann inaugurated the park on October 19, 1860 - a few months before the Civil War broke out. The Board of Park Commissioners hired Howard Daniels to design the landscape and John H.B. Latrobe to design the gateways and the alterations to the Rogers mansion. The same George A. Frederick who later designed Baltimore City Hall provided the Moorish and Chinese-style pavilions that dot the park.

Druid Lake, built in 1863 in the southern end of the park, is one of the largest earthen-dammed lakes in the country. For more than 160 years it served as a reservoir for the Baltimore public water system. In 2024, that function ended; two large underground tanks at the western end of the lake now hold the city's drinking water, and the open lake serves as scenery rather than supply. The northern end of the park was never landscaped - it remains some of the oldest forest growth in the state of Maryland, a piece of pre-colonial woodland preserved by the simple decision not to clear it. When the park opened in 1860, Baltimore was a port city of about 215,000 people whose northern edge ran roughly at North Avenue. Druid Hill sat on the wooded outskirts of town. The city kept growing around it. Today, the park is surrounded by Reservoir Hill, Hampden, Woodberry, and the working-class neighborhoods that grew up around the Jones Falls mill industry.

Druid Hill Park's recreational facilities were segregated from the day the park opened. By the early 1890s tennis had grown popular in Baltimore and Washington, and the American Tennis Association - founded specifically to develop Black tennis players in the face of exclusion from white clubs - held its first national championships at Druid Hill in August 1917. ATA membership grew steadily through the early 20th century, producing players like Althea Gibson who would later integrate professional tennis. But the white-only court signs at Druid Hill stayed up for another three decades. The 1948 protest changed that. The twenty-four arrested players — Black and white together — became the catalyst for a court fight that eventually desegregated Baltimore's public recreation facilities. Mencken's final column treated the city's defense of segregation as both legally indefensible and personally embarrassing - the kind of thing, he wrote, that should make any educated Baltimorean ashamed.

The Maryland Zoo in Baltimore, originally the Baltimore City Zoo, opened in Druid Hill in 1876 - making it the third-oldest zoo in the United States, after Philadelphia's and Cincinnati's. The Mansion House, the original Rogers estate home built in 1801, became the zoo's administrative building. The Howard Peters Rawlings Conservatory and Botanic Gardens, with its iron-and-glass Palm House and Orchid Room, opened in 1888 and remains one of the oldest steel-frame and glass greenhouses still in continuous operation in the country. Around the park sit the playful architectural follies George Frederick designed in the 1860s - a Moorish Tower at the southeast corner, a Chinese Pavilion on Swann Drive, a Sundial Pavilion. The 30-foot Wallace Monument honors the medieval Scottish rebel William Wallace, an unusual subject for a Baltimore monument that reflects the city's nineteenth-century Scottish and Scotch-Irish communities. Monuments to Wagner, Columbus, and Washington stand at various points throughout the park.

Locals call it Dru Hill - the Baltimorese contraction that gave its name to the R&B group of the same name, formed in Baltimore in 1992 and named for the park where the founding members grew up. The park survived the freeway era better than many urban parks. Interstate 83, the Jones Falls Expressway, cut along its eastern edge but did not slice through the middle. Today the park holds the Jones Falls Trail, an 18-hole disc golf course, swimming pools, tennis courts that anyone may use, ballfields, almost a dozen historic shelters, and a Baltimore Model Safety City where children learn pedestrian safety in a miniaturized downtown. The park is still being added to and slowly rebuilt - the old aquarium building, originally a pumping station that briefly housed Baltimore's first aquarium from 1938 to 1948 and then the zoo's reptile collection until 2004, sits vacant, awaiting a new chapter. Druid Hill keeps shifting. What stays is the lake at the top of the hill, the oldest woods at the north end, and the names cut into the marker by the conservatory.