 When counties were established in the British colony of New York in 1683, the present Oswego County was part of Albany County.This was an enormous county, including the northern part of what is now New York state as well as all of the present state of Vermont and, in theory, extending westward to the Pacific Ocean.This county was reduced in size on July 3, 1766 by the creation of Cumberland County in the British colony, and further on March 16, 1770 by the creation of Gloucester County, both containing territory now in Vermont.