The lower section of secondary fencing, shown here on Aug. 16, 2017, is made of thickened sheets of metal with small holes. These sections are spotted with patches because migrants often cut through the metal to get into the U.S. (Brandon Quester/inewsource)

Using previously undisclosed data from the federal government, KPBS and inewsource created an interactive map that shows every mile of the current wall along with when it was constructed. We layered that information with illegal immigration patterns and enforcement over the decades.

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