Gaithersburg is a city in Montgomery County, Maryland, United States. As of 2008, the city had an estimated total population of 58,744, making it the fourth largest city in the state behind Baltimore, Rockville, and Frederick. Gaithersburg is located at 39°8' North, 77°13' West, to the northwest of Washington, D.C. , and is considered a suburb and a primary city within the Washington-Arlington-Alexandria, DC-VA-MD-WV Metropolitan Statistical Area. Gaithersburg was incorporated in 1878. Gaithersburg is urbanistically diverse, encompassing a historic Old Town, which serves as its town center/downtown, multiple new urban communities, high-rise apartments, and many suburban subdivisions. The National Institute of Standards and Technology (NIST) is headquartered in Gaithersburg. Other major employers in the city include IBM, Lockheed Martin Information Systems and Global Services business area headquarters, MedImmune (recently purchased by AstraZeneca), and Sodexo. The city is also the location of the 220th Military Police Brigade of the United States Army Reserve.