Robert Caldwell was born in Pennsylvania in the early 1800s, and moved to Penn Township, Pennsylvania, in 1848. He constructed a mill at nearby Milltown, which he operated until his accidental death on March 13, 1871. He and his wife, Catherine Klingsmith, had four children: Sarah Jane, Samuel, Margaret, and Washington.
Washington Caldwell was born in Manor Station, Pennsylvania, on March 11, 1842, and lived in Penn Township for most of his life. He became a carpenter and farmer, later serving as a justice of the peace for Allegheny County. He and his wife, Emma Jane Longdon, had six children: Annie, William, Harry, Howard, Clifford, Mary, and Margaret.