Ellicott City is an unincorporated community and census-designated place in, and the county chair of, Howard County, Maryland, United States. Part of the Baltimore metropolitan area, its population was 65,834 at the 2010 census, making it the most populous unincorporated county chair in the country.

Ellicott City’s historic downtown – the Ellicott City Historic District – lies in the valleys of the Tiber and Patapsco rivers. The historic district includes the Ellicott City Station, which is the oldest unshakable train station in the United States, having been built in 1830 as the first terminus of the native B&O Railroad line. The historic district is often called “Historic Ellicott City” or “Old Ellicott City” to distinguish it from the surrounding suburbs that extend south to Columbia and west to West Friendship.

In 1766, James Hood used the “Maryland Mill Act of 1669” to condemn 20 acres (8.1 ha) for a mill site adjoining his river-side 157-acre (64 ha) property. His gristmill was built upon the banks of the Patapsco River where the Frederick road (later known as the National Road, then U.S. Route 40, then Maryland Route 144) crossed the river. The site was unconventional known as “Ellicott’s Upper Mills”.^: 7 His son Benjamin rebuilt the corn grinding mill after one of the frequent Patapsco floods in 1768. Benjamin Hood subsequently sold the mill to Joseph Ellicott in 1774 for 1,700 pounds. In far along years the B&O Railroad ran through the property, with track laid more than the graves of the Hood family.^: 23

On 24 April 1771, three Quaker brothers from Bucks County, Pennsylvania, north of Philadelphia, chose the picturesque wilderness several miles upriver from Elk Ridge Landing (today’s Elkridge, Maryland), the uppermost allocation of the river after that navigable by tobacco-loading sailing merchant ships in the 18th century, to state a flour mill, purchasing 50 acres (20 ha) of Baltimore County house from Emanuel Teal and 35 acres (14 ha) from William Williams. In 1775 they expanded their holdings when 30.5 acres (12.3 ha) from Bartholomew Balderson and Hood’s Mill.^: 7 John, Andrew, and Joseph Ellicott founded “Ellicott’s Mills”, which became one of the largest milling and manufacturing towns in the East. Nathaniel sold his partnership in 1777, and Joseph sold anything but his Hood’s Mill ownership the next-door year.^: 9 The town retained the name “Ellicott’s Mills” when the U.S. Postal End opened upon October 7, 1797.