Cool Hollow House, Federal and Greek Revival house in Washington County, Maryland.

Cool Hollow House is a two-story brick dwelling five bays wide with a central entrance, built c.1823 in a Greek Revival/Federal transitional style. Its walls are 16 inches thick and use American bond at all elevations, with wooden lintels and corner blocks above the windows. It stands on the National Road in Washington County, Maryland.

The house was built in 1823 during a period of stylistic change in American architecture. During the Civil War in 1863, it served as a campsite for Union troops retreating from the Battle of Gettysburg.

The property name comes from the hollow of Antietam Creek beside it, and the assembled farm was called Cool Hollow by 1861. The land patents it absorbed carry names such as Cadiz, after the Spanish city, and Chaney's Delight. The house stayed with Benjamin Emmert's heirs until 1910.

The house stands on the north side of the National Road (Old National Pike) in Washington County, with the Antietam Creek and its old ford nearby. The property is a private historic residence rather than a staffed museum, so there are no guided tours or set opening hours; view the brick facade and setting from the road.

The land patents beneath the house are older than nearly all others in this part of Maryland: only 16 of more than 2,250 patents in the area predate "Macklefish's Ridge" and "Chaney's Delight", both c.1738. One patent, "Cadiz" c.1759, took its name from the Spanish city.