why does the horn come on and stay on when key is turned off?

What is your question?

2007 Ford Explorer Sport Track. This started 4 years ago but, just once in a while. Now it happens regularly. Why will the horn stay on when the key is shut off? It takes several times of off and on to get it to turn off. This is a problem that keeps getting worse!! I usually turn off defroster/radio before I turn the key off. I can restart the truck and move the gear shift up and down, and try to turn the key off, even move the truck forward and backward. But, still when I turn the power off the horn blairs and it is embarrassing!

How long has your 2007 Ford Explorer Sport Trac had this problem?

about 4 years ago and keeps getting worse