Trademarks are fascinating things. Many folks don't realize that each state in the US also has a trademark registration system in place. While national ones are useful, there are some trademarks that are only needed for a small area like a state. Think about a small plumbing company that has a particular logo. They're not a national brand, but they want to prevent other plumbers in Colorado or Texas from appropriating the logo and the associated good will, which is something that can be added to a corporation's accounting books.
The state-based systems are much cheaper to use, although all it prevents is someone from using your trademark with that state. I own a trademark for a publishing company and it cost only fifty bucks. If someone attempted to register a similar trademark at the federal level, the previously existing state trademark can be used to show previous and active use. Then someone can go ahead and spend the big bucks for the federal version if needed. Getting a federal trademark will run you around $1500 each, including fees and legal fees. Note that each piece needs to be registered, like a logo and a tag line. If you can, keep everything together to prevent multiple fees for each piece.
If you're bored, you can actually scroll through the TESS system, which is the federal trademark electronic search system. Some folks jump on expiring trademarks and turn a profit.
Directions for registering trademarks or searching the system are available at the official website:
If you just want to search, the direct link to the TESS database is: http://tmsearch.uspto.gov/bin/gate.exe?f=login&p_lang=english&p_d=trmk
Back in the early days of metalwork and art, artisans and specific businesses used small marks on their products to show that the item was legitimate. These marks ranged from a signature to a tiny impression in the materials. Of course, cheap knock-offs were rampant until the governments began registering and allowing legal action for interlopers. Folks from Paul Revere, who was a silversmith by trade, to status-minded companies like Tiffany use specific marks to indicate something is an original. If you watch shows like Antique Roadshow, you'll hear the experts talk about trademarks all the time.