You ought to know!

"Two out of every three Americans lives in a border zone, where agents from U.S. Customs and Border Patrol can demand they produce papers.
C.J. Ciaramella writes in the May issue of Reason:
Odds are, if you're reading this in the United States, you live within a zone where U.S. Customs and Border Protection (CBP) agents have the right to stop you and ask if you're a U.S. citizen or resident.
The Immigration nand Nationality Act gives the CBP authority to operate without a warrant within a "reasonable distance" of the U.S. border.
In 1953, the Justice Department defined "reasonable distance" as 100 miles—a number that has never been revisited since, even though it means a huge chunk of the country is now a "border zone" where U.S. citizens can be stopped and questioned."