I've found a Charles DeWalt with a wife Mary in 1880, and Dinah in 1900, but he is black.If your ancestor was black it is a good idea to mention that in your post, then we can eliminate others and it helps to narrow down the search.
1880 census Polk Co, TX:
Category: Name;Relationship to head ofhousehold; Marital Status; Gender; Race; Age; Birthplace; Occupation; Father's Birthplace; Mother's Birthplace.
Mary DEWALTWifeMFemaleMU24TXKeeping HouseSCSC
1900 census Polk Co, TX:
DeWalt, Charles, h, b Mch 1852, 48, m 14 yrs, b TX, VA, SC
" Dinah, w, b Mch 1866, 34, m 14 yrs, 8 ch, 6 lvg, b TX, TX, TX
" Ida, d, b Mch 1892, 8, b TX
" Minnie, d, b Sep 1893, 6, b TX
" Eugene, s, b Feb 1895, 4, b TX
" Charles, Jr., s, b Jul 1889, 11/12, b TX
Now, if this is your family, Charles & Mary are on the 1870 census with what looks like many of his family around him.Right in the middle of the black Dewalts is a Karr Dewalt who is white.On the 1860 census K.B. Dewalt is one of only two in the county, both white and K.B., a planter, has land 10,000 and personal 16,000, this man owns slaves.K.B. and most of his family are born in SC, as are many of the older black Dewalts.
Happy Hunting (^_^)