Within a week after commencement of the siege of Vicksburg, Lieutenant General John C. Pemberton selected one of the city's finest mansions to house his headquarters operations for the defending Confederate forces.  Originally built by William Bobb in 1835-36 in the Greek Revival style, the structure was known as "Mrs. Willis' House," at the time it was appropriated by Pemberton.  Owned by her son John Willis, it stood in a neighborhood of handsome homes on large parcels of land.  The location was ideal for the general, situated on the airy bluffs well above the stagnant marshes along the river, and close to the city's commercial and government center.

During the establishment of Vicksburg National Military Park, the significance of Pemberton's Headquarters was not lost on Union and Confederate veterans, who lobbied Congress from 1895-1899 for preservation of important sites of the campaign and siege. They sought inclusion of the house in the park's enabling legislation, but the subsequent language specifically focused the park's mission on the then rural battlefield. The legislation did, however, provide for the placement of a memorial plaque at the headquarters site. The house was designated a National Historic Landmark in 1977.

In 1890, the house was deeded to Mary Frances Cowan, and was thereafter known as the "Willis-Cowan House." In 1919, the house was sold by executors of Mrs. Cowan's estate to the Sisters of Mercy, whose educational legacy began in Vicksburg in 1860. Following the war, the religious order was allowed to return to their convent at the former Cobb House across from the Willis home. Purchase of the Willis-Cowan House enabled expansion of their facilities as their school grew. Naming the structure "St. Anthony's Hall," it was used for school purposes until sold to private concerns in 1973.

In 1990, new Federal legislation changed the interpretive responsibilities of Vicksburg National Military Park, "...to interpret the campaign and siege of Vicksburg from April 1862 to July 4, 1863, and the history of Vicksburg under Union occupation during the Civil War and Reconstruction."  This compelled the park to consider acquisition of the historic structure and its operation as a visitor contact facility to address the park's expanded interpretive mandate.

The current structure retains much of its historic fabric dating from the 1863 siege, and the proposed treatment calls for an exterior and interior restoration to its historical appearance.  A later addition to the rear of the house, built in 1919, will have its exterior preserved, and its interior rehabilitated.

An excellent addition to Vicksburg National Military Park, the property provides the opportunity to learn from and utilize the resource for enhanced interpretation of the campaign and siege of Vicksburg.