Established in 1802, consisted of the area that is now the current counties of part of Durham, Haliburton, part of Muskoka, part of Nipissing, Northumberland, part of Parry Sound, Peterborough, and Victoria.

By 1826 it consisted of the current counties of part of Durham, Northumberland and part of Victoria. Abolished in 1849.

"The townships in front of the district are all very well settled, the farms are well cleared and in a good state of cultivation, and most of the houses have orchards attached to them."⁴

"The district is peopled principally by emigrants from Great Britain and Ireland, most of whom are in good circumstances."⁴

"Population in 1842, 32,033."⁴

Newcastle District was located in South-Central Ontario.