In the early nineteenth century, German Catholic settlers began moving into the region, settling in and building homes and businesses. Their presence led to the construction of masonry structures made of locally fired bricks, including the firmin rozier store and the John Hael house. By the mid-1800s, Ste. Genevieve had more German than French ancestry. The town also benefited from the busy river port, shipping iron ore, granite, and marble. The railroad also dominated the trade in granite and marble, but the local population continued to grow.
In 1800, the population of Ste. Genevieve was estimated at around 1,163 people. About a third were mulatto or African American. Once the French reclaimed the Louisiana Territory, the population of Ste. Genevieve gradually declined. The area's economy began to become more dependent on nearby cities, which eventually led to a decline of the small town. While the city's population grew in the nineteenth century, St. Louis remained the region's main city.
In the eighteenth century, English-speaking settlers began moving into the area. By 1800, there were about a thousand residents. Nearly one-third of the population was enslaved. In 1811, the American naturalist John James Audubon moved to Ste. Genevieve to establish a mercantile business with Jean Ferdinand Rozier. Interestingly, the latter's descendants still live in the area.