If you want to stay in Canada, you need to remember you have to come home too. So there are different rules crossing into Canada and crossing back into the States.
If you
click here you will be taken to the Canada Border Services Agency. It will give you the info about crossing into Canada.
If you
click here you will be taken to the U.S. Customs and Border Protection website.
And don't forget you need a full passport or a passport card (Limits destinations but is half price.)
Click here for instructions on passports from the U.S. Department of State
I lived in Niagara Falls NY for many years and it saddens me to see how the city has become another rustbelt city. The Canadian side has faired much better than the US side due to the lack of restrictions on development in the tourist areas, and political mismanagement on the US side.
That being said, there are two campgrounds on the US side that are popular with the tourists.
The Branches of Niagara for full hookups and
Four Mile Creek State Park (electric only)
The rest I will leave for you to discover. Hope this helped.