Palmer State Park

Priest Neal's Mass House and Mill Site, also known as Paradice, is a historic Roman Catholic Church located at Bel Air, Harford County, Maryland. It is a stuccoed, 1+1⁄2-story stone dwelling constructed about 1743 by Jesuits for use as a mission before Roman Catholics obtained freedom of worship under the United States Constitution. The interior floor plan is unique in its combined function as Jesuit priests' residence and house of worship: an unusually wide center hall provided meeting space and was flanked by two chambers on the west and a large reception room on the east. On the banks of Deer Creek, is the site of an 18th-century mill which the priests used to generate money to support their endeavors. It is one of the oldest extant buildings associated with the Catholic Church in America.It was listed on the National Register of Historic Places in 1990.

Thomas Run Church, also known as Watters Meeting House, is a historic Methodist church located at Bel Air, Harford County, Maryland. It is a one-story, rubble stone, three-bay church with a slate-covered gabled roof. It was among the first structures used by Methodists in colonial America.

Kalmia is an unincorporated community in Harford County, Maryland, United States. The Husband Flint Mill Site was listed on the National Register of Historic Places in 1975.

The Churchville Test Area is a United States Army facility of the Aberdeen Proving Ground, located northeast of Bel Air, Maryland (in Harford County, Maryland, U.S.). The Churchville Test Area (39.596°N 76.253°W / 39.596; -76.253) is a hilly set of cross-country road test tracks providing a variety of steep natural grades and tight turns designed to stress engines, drivetrains and suspension systems for Army vehicles, such as the M1 Abrams tanks, M2 Bradley fighting vehicle and the Humvee. The Test Area consists of 11 miles (18 km) of interconnected roads and test courses located on 250 acres (1.0 km2), with both 3-and-4-mile (4.8 and 6.4 km) closed loop courses, mud, dust and gravel surfaces, and grades ranging from 7% to 29%. On March 21, 2007, the Army celebrated the designation of a 163.5-acre (0.662 km2) buffer-zone alongside the Churchville Test Area, in conjunction with the Harford County Government, the Harford Land Trust, and the Hopkins family. Part of the US Army's Compatible Use Buffer program, under the Pentagon's environmental protection initiative, this land-use purchase was $1.4M (US).

D. H. Springhouse is a historic springhouse located at Bel Air, Harford County, Maryland. It is a little gray stone building set into the base of a steep hill. This is a stone springhouse with a schoolroom above, 16.5 feet by 23 feet, with one narrow wall set into the bank over several fresh springs. It was built about 1816, and the quality of stonemasonry is notable.It was listed on the National Register of Historic Places in 1973.

The Scarboro Landfill is a controversial landfill in Harford County, Maryland in the United States. It is located on the property of the Harford Waste Disposal Center operated by the Harford County Government where a separate sanitary landfill is in use. An assessment of the landfills was carried out and confirmed the concerns raised by local residents. The now closed Scarboro Landfill is unlined, and it received municipal waste from 1956 until 1986. In the 1980s a number of wells had been drilled in the areas surrounding the landfill and were discovered to contain pollutants such as methylene chloride, toluene, ethylbenzene and other xylenes. A remediation program is being carried out and there is a recognised problem with volatile organic compounds.The Scarboro Conservation Area is nearby.

Deer Creek is a 52.9-mile-long (85.1 km) river in Maryland and Pennsylvania that flows through the scenic areas of Harford County and empties into the Susquehanna River, roughly halfway between the Interstate 95 bridge and Conowingo Dam. Its watershed area is 171 square miles (440 km2). Its watershed area in MD (excluding water) is 145 square miles (380 km2), with 3% impervious surface in 1994. It serves as a divider between the agricultural and urban/suburban areas of Harford County.

Dublin is an unincorporated community in Harford County, Maryland, United States. Dublin was founded in the early 19th century by George McCausland and a friend who migrated from Dublin, Ireland.

Lower Deer Creek Valley Historic District is a national historic district near Darlington, Harford County, Maryland, United States. It comprises approximately 15,020 acres (60.8 km2) in north central Harford County. The primary building material is stone taken from local quarries and used to construct houses, mills, schoolhouses, and churches. Also constructed of stone are many dependencies including springhouses, stables, tenant houses, meathouses, ice houses, and barns. The district's contributing standing structures date from the mid 18th century to the 1940s, and mostly built in vernacular styles. The valley contains approximately 350 separate historic properties.It was added to the National Register of Historic Places in 1993.

Medical Hall Historic District is a historic home and national historic district near Churchville, Harford County, Maryland, United States. The home was constructed of stuccoed stone between 1825 and 1840 and is five bays long, two bays wide, and two and a half stories high. The façade features a centrally placed door with sidelights and a rectangular transom subdivided in a radiating pattern. Also on the property is a stone springhouse which 20th century owners have converted into a pumphouse and a stone cottage believed to be a 19th-century tenant house. The property is associated with John Archer (1741–1810), the first man to receive a degree in medicine in America. One of his sons was Congressman, judge of the circuit court, and Chief Justice of Maryland Stevenson Archer (1786–1848).It was added to the National Register of Historic Places in 1973.

Finney Houses Historic District is a national historic district near Churchville, Harford County, Maryland, United States. It stretches along both sides of Glenville Road in central Harford County, Maryland. The district takes in four houses and their outbuildings erected by members of the locally important Finney family between 1821 and 1906.It was added to the National Register of Historic Places in 1989.

The Mill Green Historic District is a National Register of Historic Places listed community located in Harford County, Maryland. The district consists of a small cluster of privately owned historic homes and buildings including a historic mill. The district is located at the junction of Mill Green Road and Prospect Road. Broad Creek flows through the district. The historic district designation was established in 1993.