[3][4] Between 1850 and 1861, Jackman constructed nine clipper ships (Hussar, Whistler, Starr King, War Hawk, Charmer, Black Prince, Daring, Reynard, Fear Not), four barks (Annie Buckman, Falcon, Said Bin Sultan, and Nabob) and one schooner (Lydia).

[5][6] In 1861, Jackman secured a contract to build the USS Marblehead, a 529-ton gunboat, for the United States Navy.

[4] In 1866, Jackman constructed two oak and hackmatack screw steamers, the Ontario and the Erie, for the American Steamship Company.

On February 27, 1861, Jackman was chosen to succeed the deceased Moses Davenport as Mayor.

[10] On April 19, 1861, Jackman and a committee of citizens arranged Newburyport's first citywide memorial service following the assassination of Abraham Lincoln.