Henry, glad you found some gravel roads! Gravel, in an OSM sense, is not likely what you encountered here however. An American "gravel" road is surface=compacted in OSM. Gravel is reserved for the surface of something like railroad ballast covering a track. You will find it on BGE access roads but not too many other places. When you think 'gravel' bikes, think compacted.

There is also "fine_gravel" which may be tempting but don't use that one either. Fine gravel is slippery on a bike, you would have trouble riding fine gravel without one of those fat tire bikes. This surface is also relatively rare on improved roads but may appear on some garden type paths.