You can not carry an accessible gun in Maryland.
At your last stop before entering the state, disarm, unload the weapon (some will recommend that you empty your magazines as well), and lock it in the trunk. I have two Center of Mass lockboxes. I lock my gun in one and my mags in the other, then put both in the trunk.
On your first stop after leaving the state, kit up and feel safe again.
Do not carry a gun in the car with you, and do not store a loaded magazine with the gun. Best advice is don't have loaded mags at all.
ETA: Loose/boxed ammo in the trunk with the gun is not a problem; the only sticking point is loaded magazines. Although there is nothing specifically in the statutes about carrying loaded mags, the general consensus is that an officer of prosecutor might try to treat them as legally equivalent to a loaded weapon, therefore unlawful to transport. That's why I say the safest bet is to unload all your carry mags before entering the state.
The short version is that Maryland makes absolutely no distinction between open and concealed carry. A license in Maryland (which is pretty unobtainable for residents and absolutely unobtainable for non-residents) is a Weapons Carry Permit. Without one, you don't carry a weapon, period.
Enjoy your trip through my lovely state and my a healthy tail wind see you quickly to the far side of it.