The Maryland Motor Vehicle Administration states that the FR19 is Certification of MD Insurance.

When you register or renew your vehicle registration in Maryland, you must sign an insurance certification. Your signature acknowledges that the minimum vehicle liability insurance will be maintained throughout the registration period and the vehicle will not be driven without insurance.

The MD FR19 It can only be issued by an insurance company licensed to do business in Maryland or an authorized agent of such a company. When the MVA requests a proof of insurance, a Maryland Insurance Certification (FR-19) is the only acceptable form of verification.

Maryland auto insurers inform the MVA when your policy has been canceled, and the MVA notifies you that proof of insurance is necessary. Your new company does not automatically notify the MVA if you switch insurance providers.

I hope this information answered your question about the FR19 required in MD. If you need further information try contacting the Maryland MVA or the MD Insurance Administration.