[6] The separation of Renfrew from Lanark began in 1861, with the creation of a Provisional Municipal Council[7] that held its first meeting in June 1861.

[8] The territory was originally described in 1838 as consisting of: ...the Townships of Packenham, McNab, Horton, Ross, Westmeath and Pembroke, together with the unsurveyed lands within the District of Bathurst, and all the islands in the Ottawa River, wholly or in greater part opposite to the said Townships and unsurveyed lands...[2] In 1851, Pakenham was transferred to Lanark,[5] while Renfrew was expanded through the addition of: ...all that tract of land lying between the Western Boundaries of the Townships of Lavant, Blithfield, Admaston, Bromley, Stafford and Pembroke and the Ottawa River, and a line drawn parallel to the general course of the said Boundaries of the said Townships from the western corner of the Township of Clarendon to the Ottawa River.

[9] The final expansion of the County occurred in 1877-1878, with the transfer of the United Townships of Hagarty, Sherwood, Jones, Richards and Burns, and the United Townships of Head, Clara and Maria, from Nipissing District.

Renfrew County is known for its lakeside cottages and white-water rafting along the Ottawa River, and has more than 900 lakes.

The county is home to CFB Petawawa and gives its name to The Lanark and Renfrew Scottish Regiment.