This will be a wonderful resource when you complete it, Savanha. I have three suggestions: UTEP's Institute of Oral History has over 1,000 oral histories available. UTEP Library's Special Collections has a wide-ranging collection of borderlands collections. Claudia Rivers is its head. And finally, the El Paso Public Library has the Border Heritage Collection, which includes some great photographic collections.
Are you looking solely for collections on the U.S. side?