What great geological event explains the foramtion of the Great Lakes, the St. Lawrence River system, the Columbia-Snake River system, and Great Salt Lake?

Is this homework?

Policy here says that we are not supposed to answer homework questions .So I will suggest you instead look up on the net

'great lakes formation'

There is an interactive site that simply explains it. If you want to look further you will find that the formation of the other bodies of water you mention was from basically the same event.