In the desert northeast of Las Vegas, residents living along the Nevada-Arizona border would gather on their front porches for bomb parties or ride horses into the fields to watch as the U.S. government conducted atomic tests during a Cold War-era race to build up the nation’s nuclear arsenal.In the desert northeast of Las Vegas, residents living along the Nevada-Arizona border would gather on their front porches for bomb parties or ride horses into the fields to watch as the U.S. government conducted atomic tests during a Cold War-era race to build up the nation’s nuclear arsenal.