Kathy I think you will find there are *a lot* more than just Maryland. Actually read the other day on boating list that officers where checking the trailers at a boat ramp (in either North or South Carolina) to make sure they had hitch pins. Virginia does have a law as well under SB 646
which reads in part: "be provided with a locking device that prevents accidental separation of the vehicles."
In BC its buried deep
in the laws and its actually under #9 Misc - and funny enough its not on their nice little Towing Rules PDF or handout. LOL In BC it reads: "A tow bar shall not have a locking pin missing and shall not be cracked or broken."
The towing law websites are great for fast simple answers to the basics but many of the states/provinces if you search their full laws you will find lingo such as "device to secure the coupling" or a "secondary device" - some don't use the term locking pin. Maybe they just like confusing us!
Oregon may have something in their fine print someplace as well who knows! - but maybe not - Their little towing hand out found here
- reads in part "The draw bar then slides into the hitch receiver on the tow vehicle and is secured with a locking pin. " They also show 2 photos both with couplings with holes for a pin.... go figure! LOL
Then again it may be that some states are assuming that everyone is using an approved classed coupling which are manufactured under SAE Standards that have been around for a large number of years and as such have provisions for hitch pins. They are used to dealing with mostly stick trailers so maybe they dont think anyone has a trailer older than the SAE standard
As mentioned either way it really is a safety feature that you will be thankful for spending the money on whether its the law where you tow or not. Just ask anyone who has ever had a coupling pop off a ball.