When counties were established in New York State in 1683, the present Cayuga County was part of Albany County. This was an enormous county, including the northern part of 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, and further on March 16, 1770 by the creation of Gloucester County, both containing territory now in Vermont.
On March 12, 1772, what was left of Albany County was split into three parts, one remaining under the name Albany County. One of the other pieces, Tryon County, contained the western portion (and thus, since no western boundary was specified, theoretically still extended west to the Pacific). The eastern boundary of Tryon County was approximately five miles west of the present city of Schenectady, and the county included the western part of the Adirondack Mountains and the area west of the West Branch of the Delaware River. The area then designated as Tryon County now includes 37 counties of New York State. The county was named for William Tryon, colonial governor of New York.
In the years prior to 1776, most of the Loyalists in Tryon County fled to Canada. In 1784, following the peace treaty that ended the American Revolutionary War, the name of Tryon County was changed to Montgomery County in honor of the general, Richard Montgomery, who had captured several places in Canada and died attempting to capture the city of Quebec, replacing the name of the hated British governor.
In 1789, Montgomery County was reduced in size by the splitting off of Ontario County. The actual area split off from Montgomery County was much larger than the present county, also including the present Allegany, Cattaraugus, Chautauqua, Erie, Genesee, Livingston, Monroe, Niagara, Orleans, Steuben, Wyoming, Yates, and part of Schuyler and Wayne Counties.
In 1804, Seneca County was formed by the splitting of Cayuga County. Then in 1817, in turn, a portion of Seneca County was combined with a piece of the remainder of Cayuga County to form Tompkins County.
As of 2000, there are 81,963 people, 30,558 households, and 20,840 families residing in the county. The population density is 46/km² (118/mi²). There are 35,477 housing units at an average density of 20 persons/km² (51 persons/mi²). The racial makeup of the county is 93.34% White, 3.99% African American, 0.31% Native American, 0.42% Asian, 0.02% Pacific Islander, 0.88% from other races, and 1.03% from two or more races. 1.97% of the population are Hispanic or Latino of any race.
There are 30,558 households out of which 32.60% have children under the age of 18 living with them, 52.00% are married couples living together, 11.00% have a woman whose husband does not live with her, and 31.80% are non-families. 26.20% of all households are made up of individuals and 11.90% have someone living alone who is 65 years of age or older. The average household size is 2.53 and the average family size is 3.04.
In the county the population is spread out with 25.10% under the age of 18, 8.20% from 18 to 24, 29.70% from 25 to 44, 22.60% from 45 to 64, and 14.40% who are 65 years of age or older. The median age is 37 years. For every 100 females there are 102.20 males. For every 100 females age 18 and over, there are 101.80 males.
The median income for a household in the county is $37,487, and the median income for a family is $44,973. Males have a median income of $33,356 versus $23,919 for females. The per capita income for the county is $18,003. 11.10% of the population and 7.80% of families are below the poverty line. Out of the total people living in poverty, 14.90% are under the age of 18 and 8.20% are 65 or older.