What would cause my right front to be lower?

[randy993]

Hello all,
What would cause my right front area on my truck to be lower? I can have it on level ground and put a four foot level across the bumper supports and the right side is about an inch lower. I know this is not a very scientific way of measuring but I have always noticed it sitting like this. You can see in the photo. It has all of the stock suspension. Thanks