Although inhabited by Quitman family (and descendants) for almost fifty years after the end of the war, Monmouth and its once elegant grounds had lost its former splendor.  During the 1870s, the main house and grounds were rented out, with the land utilized for cotton crops.  By the 1880s, Quitman family members once again inhabited the estate, and although the Quitman daughters managed to restore their financial picture, with minor improvements to the estate, Monmouth remained a modest image of its former self.  After the last Quitman daughter Annie Rosalie and granddaughters died, Monmouth was sold out of the Quitman family in 1919.  Monmouth thereafter remained empty (except for an occasional tenant), housing only furniture for many years, a telling monument to a bygone era.   

      After changing hands a few times, Natchez widow Annie Shotwell Green Gwin purchased Monmouth in 1922.  Gwin, a member of a prominent southern family with plantations in the Delta and near Jackson, Mississippi, occupied the house with her three young children.  She ran a dairy farm on the place while renting out parts of it as barbed-wired pasturage and farm land.  Within a few years, Gwin married Herbert Barnum and moved to the Arlington estate house nearby.  Barnum rented Monmouth’s main house and property and later, Barnum’s adult children eventually moved into Monmouth, where they remained for several years.    

      Efforts to revitalize Natchez’s failing economy during the Great Depression in the 1930s saw the advent of a newly realized tourism industry by the local garden clubs.  These tours centered on the town’s antebellum mansions, where Natchez women decked out in gowns and bonnets showed off their mansion houses. Moreover, tourists from all over the country paid to see these relics of a bygone era.  Annie Barnum was one of the founding members of the Natchez garden club and she opened Monmouth to tourists during the spring pilgrimage season.  Monmouth, Arlington and other mansion houses in Natchez, became a curiosity—a haunting reminder of days past, despite various stages of  deterioration (or perhaps because of it).   

      With minimal attention to its upkeep, Monmouth continued to decline over the subsequent years and eventually was removed from the tour.  After Annie Barnum’s death in1960, her children, Lucien, Lawrence and Anne offered Monmouth for sale.  There were no buyers.   

      In 1972, a Natchez Metropolitan Planning Commission report described the house as sorely “neglected.”  Litter polluted the house and surviving structures, the grounds were more overgrown than they had been at the end of the Civil War.  Paint peeling from Monmouth’s distinctive front columns stood witness to not only the decay of one of the Old South’s most graceful homes, but also to the chipping away of Monmouth’s rich history.