Official photo ID (state-issued driver license or ID card) and
proof of citizenship (sealed birth certificate, meaning the kind with the "raised bumps" where the county clerk used the official embosser) are all you need if you don't have a passport and you're traveling by land. This is good for both the US side and the Canadian side.
We travel thru Ontario going from Michigan to NY state and back to visit MIL just outside of Niagara, and we have only ever had trouble the very first time, back in 2002, when it didn't occur to us that passing through Canada was "entering a foreign country". (When the Canadian customs agent made that statement, it took all my willpower to keep from saying, "we're not going to a foreign country, we're going to CANADA, for crying out loud!"

Growing up in Michigan my entire life, Ontario is "right next door" and doesn't seem "foreign" to me at all, other than the money looks kinda funny compared to ours!

)
Particularly when crossing at Niagara, they're used to lots of tourists coming and going, and they're pretty nice there. (got into a very pleasant conversation with a US agent at 3:00 a.m. once, discussing our MILs)
Sometimes they don't ask to see your papers, but if they DO ask, you'd better have them or they "strip search" your poor vehicle!

(that's what happened the very first time... and we have always made sure to have birth certificates with us ever since, and nary a problem)