is a census-designated place (CDP) in Howard County, Maryland, United States. The population was 22,042 at the 2000 census. Founded early in the 18th century, Elkridge is located at the confluence of three counties, the other two being Anne Arundel and Baltimore counties. It is bordered on the north by Catonsville, on the east by Linthicum and Baltimore-Washington International Airport, on the south by Dorsey, and on the west by Ellicott City and various small communities between it and Columbia.
Elkridge qualifies as the oldest settlement in its present county, when Howard was a part of Anne Arundel County. Its location on the Patapsco River was a key element in its growth. The settlement existed even before the Maryland General Assembly elected a law to erect a , forty-lot town at Elkridge Landing to be called "Jansen Town" in 1733. Initially, the settlement was developed as a place where planters, who each had a wharf along the river, could bring their tobacco crop to be loaded on English trading ships. Later, Elkridge Landing was built as the seaport dock for the community. In 1825, Jansen Town burned, taking out all of the oldest buildings at the Landing and 9 out of 10 houses in the village.
Elkridge has historic churches, including Melville Church on Furnace Ave. Its original building was the first Methodist church built (1772) and was visited on the circuit rides of Francis Asbury. Saint Augustine Church, on Old Washington Blvd., was originally built in 1845.
Elkridge had a rich history of industries including pig-iron forging, basket weaving, paper, cotton and grist milling, as well as employment from the B&O Railroad. The Thomas Viaduct, located over Levering Avenue at the entrance to the Patapsco Valley State Park, is the oldest stone curved bridge in the world. Built in 1833, its architect was Benjamin Latrobe, Jr. The B&O first used horse-drawn coaches in relays, hence Relay Station was added. The viaduct also carried the Tom Thumb, and the first telegraph message from Washington, D.C., stating "What has God wrought?" was wired across.
Elkridge did not escape the Civil War. Union troops guarded the viaduct and the thoroughfare to Baltimore City by camping on Lawyers Hill, a community of summer estates built over the years by residents such as Caleb Dorsey ("Belmont"), Baltimore City Supreme Bench Judge George Washington Dobbin ("the Lawn"), Thomas Donaldson ("Edgewood"), John Latrobe ("Fairy-Knowe"), and the Penniman family home ("Wayside"). Some of these families had slaves. Their estate cottages were built along the very top of the Lawyers Hill, including along Old Lawyers Hill Road, on which at one corner stands the Elkridge Assembly Rooms. This community hall, built in 1871, was a neutral meeting place for entertainments for Northern and Southern sympathizers of the neighborhood and owned by them as stockholders. Neighbors did not betray neighbors and each protected others' property from advancing troops. The historic Lawyers Hill homes remain in the National Historic Trust.