Canadians and Americans are allowed to bring as much as they like when they cross the border. However, only a portion of what is brought into the U.S. (or into Canada) is considered free of taxes and duties. The portion that is tax and duty free is called a customs allowance.

200 Cigarettes
50 Cigars
200G Fine Cut Tobacco

1.0L of wine, beer, liquor or ale

$100CAD to be left in U.S.A.

Subject to duties and taxes

150mL of alcoholic beverages

$200USD per person