Fremont Street in Las Vegas. Best known these days for its four-block, LED-canopied pedestrian mall (Fremont Street Experience), the Nevada city’s pre-Strip focal point for casino gambling has also become something of a memory machine. For well over a decade, the Neon Museum has been building its collection of significant but unwanted signage. Las Vegans did not invent neon signs. That honor goes to an early 20th-century French inventor, Georges Claude, who pioneered the electrification of neon in glass tubes. But nowhere has neon been more central in forging an image than in Sin City, which wowed midcentury visitors with garish, larger-than-life signs that towered above the low-slung architecture of the casinos and motels they advertised. As Las Vegas entrepreneurs added ever more elaborate…