Your George Henry Alexander may have been in Wise County in 1870-- but he may have been east or south of there, too. Many early settlers of Wise County moved a county or two eastward around 1870 because of the unsettled situation after the Civil War. Then when things calmed down, they moved back to Wise County. Of course, some of them moved into the eastern portions of what is now Oklahoma and missed all censuses whatsoever. I do have family members, though, that were in Wise and Palo Pinto and Erath counties in 1870 who the census takers just missed. Perhaps the census takers feared running into a Comanche war party? For example, Jonathan Hemphill Walker, wife Rebecca, their children, and their childrens' families were in the Wise and Parker county areas by the middle 1850s. They remained in Wise County through the Civil War, but in 1870 many of them were enumerated or doing business in Grayson County, Dallas County, Denton County, etc. The survivors were back in Wise County by the 1880 census.