Most Americans are accustomed to carrying around a driving license, which serves day-to-day as id for cashing a cheque, etc. Here is Texas you can also get an id from the department of public safety, for your convenience, if you don't have a driving license.

No one is required to carry an id, but we are required to carry a driving license while driving.

The alternatives to the police establishing a suspected prowler's identity and verifying their story are: 1. Believe whatever story the prowler tells them (which doesn't seem like a good idea since some prowlers really are criminals) or 2. take everyone down to the greybar hotel and let a judge sort it out later (which doesn't seem like a good idea since some suspected prowlers are really not criminals).
- Phil