Where are the highest areas of elevation in Texas? (Details follow)

I am not talking about one hill…I am wondering if Texas has an area that is high in elevation and high above sea level. Someone asked me and I didn’t know…I always think of Texas as flat (except for the Hill Country.)

I know that the Hill Country must be an area that is high above sea level (possibly?) But are there other areas? If so, how high are they? (I am sure some Texans may well know the answer to this.)

Thank you in advance.