I think the Maryland legislature did reject secession.
Walt
Maryland could not seceed without Virginia committing to secession, the position would have been militarily untenable.
Hordes escaped to Virginia, sometimes forming their own units (the First MD Volunteers was one), sometimes enlisting in existing units, but fighting for the South.
Yes, admittedly, some went for the Union, but they were the minority, and mostly from the northwestern part of the state (above the fall line).