News from the U.S.-Mexico border is happening almost daily. President Trump has been emphasizing a new wall since the 2016 campaign, and prototypes are being developed. Trump has also called for putting National Guard troops on the border, and Arizona Gov. Doug Ducey—for one—has sent some there already.

Tension because of the border and immigration has been around for decades. In her new book, Porous Borders, Arizona State University Assistant Professor Julian Lim looks at how the early part of the 20^th century in El Paso, Texas, helped frame some of the debate that is occurring today. Professor Lim joined The Show on Thursday.