Crockpot Taco Soup

1-lb ground beef
1 large onion, chopped
3 (14-oz) cans pinto beans (I use black beans as that is my favorite)
14-oz can tomatoes w/ chilies (I used my homemade mexican style version)
14-1/2 oz can petite diced tomatoes
15-oz can tomato paste
1 pkg dry ranch dressing mix
15-1/4 oz can whole kernel corn, drained (I used 3 large fresh ears of corn as that's what I had on hand)
2 c water

Brown beef & onion in a medium size skillet. Cook until meat is no longer pink & onions are translucent. Drain grease. Combine meat & onion with remaining ingredients in a 4-6qt crockpot. Cover and cook on LOW for about 4 hours or until ingredients are heated through. Serve with tortilla chips if desired.