If the trailer has a VIN on it, you are probably going to need a title. You might get away with registering as home made but that pretty much depends on how strict about doing so Maryland is.
I'm in CA, so it may be a lot different. I found an agency who will do registration for you for a fee. They helped me with issues around both boat and trailer title. For a fee... and I didn't have to figure out the DMV stuff.
