A makeshift memorial to Hispanic Civil War Union soldiers in an isolated part northern New Mexico is a typical representation of sites linked to U.S. Latino history: It’s shabby, largely unknown and at risk of disappearing. Across the U.S, many sites historically connected to key moments in Latino civil rights lie forgotten, decaying or endanger of quietly dissolving into the past without acknowledgment. Scholars and advocates say a lack of preservation, resistance to recognition and even natural disasters make it hard for sites to gain traction among the general public, which affects how Americans see Latinos in U.S. history. The...