Maryland has updated its uninsured motorist provisions as of July 1, 2018.
Maryland Annotated Code Insurance Section 19-509.1 - Enhanced Underinsured Motorist (a/k/a "stacking" by lawyers and those in the insurance industry). Enhanced Underinsured Motorist (EUIM) coverage can be added to new auto policies issued in Maryland as of 7/1/18. EUIM coverage will provide better protection to any occupant of a vehicle insured in Maryland when injured due to an at fault driver who is underinsured. You might be able to also add EUIM coverage on existing Maryland auto policies as of 7/1/18 depending on your auto insurance carrier.
I encourage you to call your auto insurance company or agent and inquire about Enhanced Underinsured Motorist Coverage (EUIM) And see how it benefits you and whether you should add it To your existing auto policy.