McClernand's Corps, immediately upon debarking on April 30, headed for
the bluffs 3 miles inland. By nightfall the Federal soldiers had reached
the high ground and pushed on toward Port Gibson, 30 miles south of
Vicksburg. From this point, roads led to Grand Gulf, Vicksburg, and
Jackson. Maj. Gen. John S. Bowen moved his Grand Gulf command toward
Port Gibson to intercept the threat, and, at daylight on May 1, leading
elements of the Union advance clashed with Bowen's troops, barring the
two roads which led to Port Gibson.
The battle of Port Gibson was a series of furious day-long engagements
over thickly wooded ridges cut by deep, precipitous gullies and covered
with dense undergrowth. While greatly outnumbering Bowen, McClernand was
prevented by the rugged terrain from bringing his whole force into
action. Slowly forced backward, Bowen conducted an orderly retreat
through the town, which he evacuated. The holding action had cost Bowen
800 casualties from his command of 8,000; Union losses were about the
same from a force at hand of about 23,000. Pemberton determined not to
contest Grand Gulf lest he risk being cut off from Vicksburg and
withdrew across the Big Black River. Thus he permitted Grant to occupy
Grand Gulf and gave him a strong foothold on the east bank of the
Mississippi.