[3] In 1850, the Newcastle District was reorganized into the United Counties of Northumberland and Durham, an arrangement which lasted until 1973.

Northumberland County has various cycling, hiking and other outdoor trails.

[14] The Northumberland portion of the Trans-Canada Trail spans from Hastings to Hoard's Station in Campbellford, following an abandoned rail line.

There are five signed bike routes: Glorious Ganaraska, Rice Lake Ramble, Shelter Valley, Presqu’ile Promise and Trent River Truckin'.

[15] The Northumberland County Forest offers various trails available for hiking, cycling, horseback riding, ATVing, off-road motorcycling, cross-country skiing, snowmobiling, snowshoeing[16] as well as a 3.2 km, accessible Universal Trail.