Mary,
I can help you with the 15th Texas cavalry unit. Do not confuse this with the 15th Texas Infantry. The 15th Texas Cavalry unit was orginized in Dallas in Febuary of 1862 from units from San Antonio and Denton. It picked up other units in the north Texas area. My ancestor lived in Hunt County and became a member as it passed through Hunt county on its way to Clarksville. Let me know what you need to know and I will try to help.