Some places in Texas are unambiguous. When you’re in say, San Antonio, Marfa or Galveston, you just know it. But in other parts of the state, the boundaries are less well-defined.

For example: How do you know when you’re in West Texas?

Producer Michael Marks set out to tackle this question.

After a long and winding road – that included some pit stops with the Texas Standard staff – he found the answer in a surprising place: a map of oak tree growth in Texas.