A part of De Witt's Colony, 1825-1836. A part of Gonzales County to 1848. First settlements were on Plum Creek and the San Marcos River. Created March 6, 1848; organized August 7, 1848. Named in honor of Nathew Caldwell, "Old Paint," 1798-1842, soldier-statesman. Signer of the Texas Declaration of Independence, Commander of the Texas Rangers. Lockhart, the county seat.