Harrisburg Air National Guard Base is a United States Air Force base, located at Harrisburg International Airport, (IATA: MDT, ICAO: KMDT, FAA LID: MDT) Pennsylvania.

The first airplanes landed in 1918 at Middletown Air Depot, when it was under the administration of the Signal Corps of the United States Army.

Middletown had an abundance of engine and airframe shops and a supply distribution system that made it a significant facility, but a poor runway that, it was felt, would be too expensive to improve.

The installation was renamed in honor of 1st Lieutenant Robert Sanford Olmsted, U.S. Army Air Service, on 11 March 1948.

First Lieutenant Olmsted was killed in a ballooning accident over the village of Loosbroek, Netherlands on 23 September 1923 while competing in the Gordon Bennett Cup.

[2] In addition, in 1966, much of the former Air Force property was converted into The Pennsylvania State University—The Capital College, otherwise known as the Harrisburg Campus.