You mentioned you had your answer, but here is just a bit more info.

Below is info copied from the Texas Insurance Code and Basic Manual for Title Insurance. 

In Texas, in order for a title policy to be issued, the title search must be done from an underwritten minimum 25 year geographically indexed title (abstract) plant per Texas law (with exceptions to this rule if certain circumstances exist).  Below is the definition from the Basic Manual (with hypelinks to the Insurance Code) 

i.   Abstract Plant---A geographically arranged abstract plant, currently kept to date, that is adequate for use in insuring titles, so as to provide for the safety and protection of the policyholders. An abstract plant as further defined in Rule P-12 and as further provided for in the Insurance Code, Article 9.02 (f) and Article 9.30, must include an abstract plant for each county in which a title insurance agent or direct operation maintains an office.