US companies with more employees than anyone else

You know that old saying, "it's not the size of the boat, it's the motion of the ocean", well these folks listed here didn't get the memo — they're some of the largest USA employers. On the other hand, more people can mean more power, more presence and greater (implied) stability. But whatever way you cut it, what you can't do is ignore these companies. Chances are, you know someone working for them.