west of _________to New Mexico and Sante Fe County back to New Mexico. The Western border of Texas extended along the Rio Grande to the city of: __________. (page 13).

It seems like you're referencing a passage that pertains to the geography of New Mexico and Texas. To fill in the blanks, it would likely read:

"west of Texas to New Mexico and Santa Fe County back to New Mexico." The Western border of Texas extended along the Rio Grande to the city of: El Paso.

Please adjust based on the specific context or source you're referencing if needed!