A Canadian who marries a US Green Card holder (permanent resident) or US citizen is eligible to become a permanent resident. Such Canadians are in a fortunate position: once they receive their Green Cards, they no longer need to limit the number of days they spend in the US each year, and they are able to legally work in the US.
To begin the Green Card application process, Form I-130 must be filed with United States Citizenship and Immigration Services (“USCIS”), along with payment of a fee and a variety of documentation, including your marriage certificate.
Application for permanent residency can be made while you are inside or outside the US. However, there are good reasons to apply from within Canada: you may prolong the process and limit your ability to travel outside the US if you choose to file the I-130 application while stateside.
Once granted permanent residency, although you will be able to permanently live and work in the US, you will not be able to enjoy the same rights as US citizens, who can vote in elections and receive important tax and estate planning benefits.
As a US Green Card holder, you eventually have the option to become a US citizen via the naturalization process. Becoming a US citizen has cons as well as pros, though; we therefore recommend weighing all factors in a considered fashion before making the decision to become a US citizen.