McNab was not a United Empire Loyalist, since they were veterans of the American Revolution, but as a veteran of the War of 1812, he was similarly entitled to a grant of land. He was born in Barnet, Caledonia, Vermont on 9 July 1787. He arrived from Vermont about 1805  and after the war lived in Toronto  where he later married his wife, Sarah Marsh. When the area around Esquesing (later Norval) was opened for settlement in 1819, he obtained a land grant and moved his family there. He set up a grist mill and saw mill on the Credit River. He later sold the mills and moved to Owen Sound with his wife and family. He is referred to as "Colonel James McNab" in later years due to his raising a troop of men during the 1837 Rebellion. It is said that he was unable to claim his expenses from the government and had to sell his mills to pay for the cost. He died in Owen Sound on 24 Sept. 1866 and is buried in the Greenwood cemetery there.
In 1991, a historic plaque was unveiled in McNab Park in Norval, Ontario in his honour.
- Upper Canada Land Petitions, Page 827, vol 341A, bundle M12, petition 282, microfilm 2201
- Upper Canada Marriage Bonds from the Library and Archives of Canada dated 11 Jun 1814
- Upper Canada Land Petitions, Volume: 411; Bundle: P 1; Petition: 57; Microfilm:C-2733; Reference:RG 1 L3; Page 938
- City of Owen Sound Genealogical List All Cemeteries