Parker is a city located in Armstrong County, Pennsylvania, United States. The population was 799 at the 2000 census. The city was named for John Parker, a lead surveyor of Lawrenceburg. Parker is sometimes referred to as the "Smallest City in the U.S.A.". Parker was incorporated as a city on March 1, 1873 by special state legislation in the midst of the northwestern Pennsylvania oil boom. The new municipality was called "Parker" and was made up of the earlier villages of Parker's Landing (on the Allegheny River) and Lawrenceburg (on the bluff above the river). Residents assumed that Parker would quickly become a major population center, and, at the height of the oil boom, the population of Parker grew to over 20,000. The boom quickly went bust, however, and by the 1880s the "city "returned to its historic, small village size, and a population of approximately 1,000.