I have been researching the MECUM line for 30 years and have accumulated much information on our line.

Beginning with my earliest known MECUM/MECOM:

John Mecum(Mecom), b. 1763 in N.J., married Margaret. Children: Mary, Elizabeth, Rachel, Catherine, John, David, Jonathan, Margaret, Susanna, George Washington, and unknown MECUM

Pennsneck NJ seems to be an early beginning point.