I find over 30 species of Solidago listed for Maryland. Doing a basic image search on Google there were at least 6 or 7 that appeared similar. With so many species in such a small area I would not be surprised at natural hybrids as Kent said.
Here are maps of the species that grow in the US. You can find those that grow in Maryland then do an image search to narrow it down to a few possibilities, then do more in depth on those few.
http://bonap.net/NAPA/TaxonMap...
