Ant Invasion!!!

Every year around this time we get an invasion of ants. I've been seeing a couple here and there in the kitchen but today I came home and there was a SWARM of them.. they had a trail from the floor to the top of the counter top, and the wall. It is driving me completely crazy. My house is not dirty, there is no food left out, no crumbs, I sweep the floor at least twice a day and mop once a week I have NO idea how to get rid of them at this point. This time is a little trickier because I have an 11 month old daughter and do not want to use anything that will make her sick. I need something that will KEEP THEM AWAY! any suggestions?