Porter's Fleet Shelling the Batteries Vicksburg
Union forces bombarded the city all night, from 220 artillery pieces and naval gunfire from Rear Adm. David D. Porter's fleet in the river, and while causing little property damage, they damaged Confederate civilian morale. On the morning of May 22, the defenders were bombarded again for four hours before the Union attacked once more along a three-mile front at 10 a.m.
Benson John Lossing, ed. Harper's Encyclopedia of United States History (vol. 10) (New York, NY: Harper and Brothers, 1912)