It was Grassmann who apparently persuaded celebrated Nicaraguan/Mexican artist Roberto de la Selva to paint themed murals throughout the first floor interior of the Mexican Cottage. In the late 1920s, during his first trip to the United States, de la Selva spent months in rural Union County painting the murals, which depict native Mexicans at work, play and worship, including statues of both ancient gods and the Virgin Mary. As the only murals de la Selva, who was primarily a sculptor, is known to have painted, these murals are significant to both the history of Feltville and the international art world.