Maryland's Annual Free Fishing Days
There are three Free Fishing Days in Maryland, the first two Saturdays of June and July 4th. A fishing license is not required in both tidal and non-tidal waters on these days. However, all Maryland fishing laws apply

Summary of Maryland rules on this link
http://www.dnr.state.md.us/fisheries.../regindex.html

general Info
http://www.dnr.state.md.us/fisheries/