The C&O Canal is great. Re: the best bike: newbies should be aware that some sections get rocky, rutted or muddy, and many sections have tree roots and considerable forest debris. Upstream, the path is also frequently overgrown, with the clear path reduce to a narrow track. A trail oriented hybrid is a good recommendation for longer rides and rides on the well-maintained sections, but it does require some care. On the rougher sections and in wet weather, I like a mountain or trail bike. Full suspension is overkill, but a hardtail is nice in the sloppy and rocky parts. It’s heavier, but it’s nice to be able to sail over or through the obstacles. I’m old enough to prefer the lazy man’s choice on shorter rides, but if I’m going more than 25 miles or so, I’d go with the hybrid.
Yes, the canal path has to be maintained. I was riding it during that very wet spring two years ago, went around a bend, and found the river rolling over a section of the towpath. Being prudent, I turned around, rode back and got off the towpath pronto. The Park Service guys showed up to close the trail as I was leaving. Keeping it up is an ongoing struggle. Chat with some of the maintenance guys some time when you ride past them. They are great guys, always friendly, the kind you are glad to see in a Park Service uniform, and you will get an education.
Great advice!