United States Local stamps were in use along with USPO adhesives until about 1861. The local companies were allowed to provide enhanced delivery and pickup service within cities (for businesses the Post Office usually delivered from post office to post office on intercity mail) and local companies provided the door to door service. There were scores of local delivery companies and hundreds of collectible locals varieties as listed by the Scott specialized catalog.
What has always intrigued me about US Locals is their popularity and scarcity. Aside from the Bloods company of Philadelphia and the Boyd company of New York, even the more common Locals are very scarce. No more than two or three prominent collectors of these stamps can exist in any generation. There are no dealer pools of material awaiting new collectors. And Local collecting tends to attract real philatelists who are driven by owning rarity and not just pecuniary gain. Most prominent local collectors hold their collections for decades if not their entire lives (and coincidentally, they also tend to be long lived). Thus, if you want to collect Locals and the next great Local collection comes up at Auction (and this only happens every decade or so) dig deep. Chances are you won’t see the material again for a long time.