Grenville County is a former county in the Canadian province of Ontario. It fronted on the north shore of the Saint Lawrence River, between the towns of Kingston and Cornwall. The county was created in 1792, and named in honour of William Grenville, 1st Baron Grenville, who was the British Secretary of State responsible for the colonies in 1790. It consisted of five townships, which were settled primarily by United Empire Loyalists in the late 1700s after the Revolutionary War. Prior to being settled by Europeans, the area was home to many generations of native cultures. Grenville County merged with Leeds County in 1850 to create Leeds and Grenville County. The county covered an area of 272,261 acres (110,180 ha).

Lanark County is a county located in the Canadian province of Ontario. Its county seat is Perth, which was first settled in 1816 and was known as a social and political capital before being over shadowed by what we now know as Ottawa.