Orleans County is located in western New York State, between Buffalo and Rochester, on the shores of Lake Ontario. The county seat is Albion.

In 1683, when counties were established in New York State, the area presently known as Orleans County was part of Albany County. This extremely large county included northern New York, Vermont and extended westward to the Pacific Ocean. On July 3, 1766 Albany was condensed in size by the creation of Cumberland County, then again on March 16, 1770 by the creation of Gloucester County. Both counties contained territory in Vermont.

Albany County was divided again on March 12, 1772 into three counties: Albany, Tryon, and Charlotte. Tryon County contained the western portion, still extending to the Pacific Ocean. In 1784, the name of Tryon County was changed to Montgomery County in order to honor Richard Montgomery, a Revolutionary War hero. In 1789, Ontario County was formed from part of Montgomery. In 1802, Genesee County was formed from Ontario County. In 1806, Allegany County was formed from Genesee County. In 1808, Cattaraugus, Chautauqua, and Niagara Counties were created from Genesee County. In 1821, Genesee County was reduced in size again with the creation of Livingston and Monroe Counties. Finally, in 1824, Orleans County was created from what was left of Genesee County.

When Orleans County was formed, a naming dispute arose. Would it be named after Andrew Jackson or John Adams? It would be neither. Orleans County was named in honor of the French Royal House of Orleans.

As of 2000 census, the population was 44,171. The county has a total area of 817 square miles. 391 of it is land and 426 (52.12%) of it is water. The large area of water is due to the extension of Orleans County north into Lake Ontario to the Canadian border (running through the middle of the Lake Ontario). The Erie Canal runs through the county.