I learned today that if you're an American and you go to Canada that your cell phone should still work.

You may get some roaming charges bolted onto your bill however.

Addendum 5/13/2015: I pen this inside of Canada and I have now been through the roaming charge experience. I will need to call Verizon wireless when I am back stateside to turn off the roaming plan I turned on. As soon I as I was over the border they texted me with a number to call to get my phone to work anew. (It has stopped working outright.) Using iOS 8.1.3 (12B466) at my iPhone 4S I had to ultimately go into Settings > General > About to read off the ICCID number to the party with Verizon on the other end of my phone call. I had to go into Settings > Cellular > Roaming to explicitly turn on "Data Roaming" too in order to shove vacation photos up to Facebook.