UNITED COUNTIES OF NORTHUMBERLAND AND DURHAM, ONTARIO

The 'United Counties of Northumberland and Durham' was a historic county in the Canadian province of Ontario. The two counties were originally combined in the District of Newcastle formed in 1798, and continued with joint administration until January 1, 1974 when portions Durham County were amalgamated with adjacent Ontario County to form the Regional Municipality of Durham. At this time, Northumberland County reverted into a standalone county, and Durham County was dissolved.