Key won't turn...why?

What is going on? My 2001 Impala key will not even turn in the ignition? The steering wheel is not locked. What to do?

is it in gear?

If the car is still in gear, you won't beable to get the key out of the ignition, but it will still turn, and the car won't start. Did you try giggling it around alittle while you are trying to turn the key? The steering colum doesn't lock, so it's not that. Either make sure you have the right key for that car(if you have another GM car). Did you try the other key that you might have for that car??? Maybe there is something wrong with that key.

Let me know
mike