Any map-lovers looking to lose track of time for a few hours should say hello to the newly-arrived USGS Historical Topographic Map Explorer, which allows users access to a treasure trove of maps of cities across the nation and lets users load multiple maps and toggle the transparency of each, so you can see the old map overlaid on the map of today. Go back to the turn-of-the-century maps of Los Angeles to find the old ranchos, or to the '40s and '50s to see old Pacific Electric lines. Compare pre- and post-Dodger Stadium maps of Elysian Park; see cartographic evidence of the lake at Westlake Park before it was split in half by Wilshire Boulevard, or of Los Feliz spelled Los Felis. It's all here, for the casual, time-sucking perusal of the public. We've collected a few of our favorite greater Los Angeles details into a handful of colorful before-and-afters below. We'll look closer at specific neighborhoods in the coming days.