Hi - There are an incredible number of Keith's named in a 1914 publication called HISTORY OF DUBLIN (Dublin TX is in Erath Co)that I purchased through the Dublin Historical Society - and is still sold there.
It begins in the 1850's and some of the names are Jonathan Keith, Nick Keith, 'Muley' Keith, William ('Big Bill') Keith, Grandpa Keith. One of the first marriages was between Sarah Eveline Keith and C.M. O'Neal.
There are many more than those listed above - and I believe the publication mentions that at one point, there were more Keiths than any other surname in the population. The information covers about a thirty-year period - and Keiths were prominent in the development of the town. They helped establish schools, fought Indian raids and helped a native American in distress. Quite impressive.
Hope this helps those of you looking for your Texas-connected Keiths.