The 1880 census is online at http://www.familysearch.orghttp://www.familysearch.org -- that is the LDS or Mormon website.That index is very user friendly and spoils us for other census indexes.First off it is an everyname index, not just head of household.Then it will bring up other surnames with similar spellings, often you can learn ways to look for your family on other records with this help.And, if that wasn't enough, it will bring up common nicknames.If you put in Mary, the females named Polly will also show, as that was a common nickname for Mary.
I have access to Heritage Quest online through a local public library, check and see if any of the libraries in your area have the subscription.Not all censuses are indexed on HQ, yet.I have dial-up service so it wasn't fast, it plugs along and I'm thinking of taking up knitting.LOL
Now, on the 1880 census, older children were born in MO, so went looking for family on MO censuses.
Have you used GenWeb sites?If not, let me know I'll give you some hints for them.
Look for county histories where your family lived.Check out land records.Many of these items, if not online, may have been microfilmed by the Family History Library in Salt Lake City.See if you have a Family History Center near you.You can order out film and fiche to the local FHC, for a nominal fee, then look at the filmed copies of old original records.That sometimes can get thrilling.You never know what you will find in land records -- besides the description of the boundaries of the land.(^_^)