In 1802, Spalding sold his plantation on St. Simons Island and began purchasing land on
Sapelo Island. By the time of his death in 1851, Spalding and his family owned all of Sapelo Island with the exception of 650 acres at Raccoon bluff. While primarily known for his Sapelo Island plantation, Spalding also owned real estate and plantations elsewhere in Georgia. In 1822, he purchased
Hutchinson Island across the Savannah River from Savannah, Georgia along with 125 slaves to work the rice fields on the island. He later sold his Hutchinson Island property in the 1840s. He also owned a plantation on
Black Island near Darien, Georgia. Soon after purchasing his Sapelo Island plantation, Spalding hired
Roswell King to be the overseer of the crew of slaves that were to construct a mansion on the south end of Sapelo Island. The mansion completed in 1810, known as South End House, would go on to survive being damaged by a
destructive hurricane in 1824 before being heavily damaged during the
American Civil War. Decades later, the mansion was repaired and enlarged later by a later owner
Howard E. Coffin and then again by
R. J. Reynolds Jr. The mansion is currently owned by the state of Georgia and is now commonly referred to as the Reynolds Mansion. Thomas Spalding was also noted for his scientific approach to agriculture and was a frequent contributor to
The Southern Agriculturist,
The American Agriculturist, and
The Southern Cultivator In order to further the study of agricultural science, Spalding became one of the founders of the Union Agricultural Society of Georgia in 1824 and was its first president. He thoroughly believed that knowledge of improvements in agricultural science should be freely shared. Spalding engaged in the cultivation of a wide variety of crops on his Sapelo Island plantation. He was noted for being one of the largest producers of
Sea Island Cotton in the state and wrote extensively on its cultivation and its history. Rice was also grown on his Sapelo Island plantation, but not to the same extent as sea island cotton. Spalding is credited with introducing the
sugarcane cultivation to Georgia in 1805. Sugarcane had previously been grown for profit in Louisiana, but prior to Spalding, Georgia had been considered too cold of a climate for growing sugarcane. Due to Spalding's advocacy, sugarcane cultivation soon spread to many other plantations in coastal Georgia and inland along the banks of the
Altamaha River. Spalding constructed a number of sugar mills on his Sapelo Island plantation. All were built with
tabby walls. His earlier mill was powered by oxen. A sugar mill built in the 1830s was
tidal powered. The ruins of his sugar mills are still visible. By the late 1820s, Spalding began to advocate for
crop diversification as a way to combat the collapse in market prices of staple crops like cotton and rice. He began calling for a resurgence in the cultivation of
indigo and
silk in Georgia. Both crops had been profitable during the colonial period. He gave thousands of mulberry tree saplings away to new neighbors between 1837 and 1838 in order to increase silk cultivation. He experienced moderate success with the production of wine. Spalding also cultivated olive trees on Sapelo Island that he had imported from the
Province of Livorno in Italy, but had limited success. In 1803 a group of 75 captive Igbo people, that had been procured for Spalding and a neighboring planter John Couper, rebelled against being forced into slavery. Twelve of them committed mass suicide by drowning at what would come to be called
Igbo Landing on St. Simons Island. Some of the survivors were brought to Spalding's Sapelo Island plantation. Spalding was an advocate of the
task system of slave labor as he believed it allowed for his slaves to be more self-reliant. After the first few years of operating his plantation on Sapelo Island, Spalding switched from using white overseers to exclusively slave overseers. He summarized his theory of running his plantations as ideally being "without the interference of white man." Spalding housed his slaves in small village communities known as "hammocks" in which slaves of similar ethnic backgrounds lived together. He believed that type of community organization would better acclimate to slavery the newly enslaved people he purchased at
Charleston, South Carolina, who were just arriving from Africa. In 1830, he owned 400 slaves. In 1840, he owned 348 slaves. In 1850, he owned 293 slaves. Spalding's primary slave overseer was a slave named Bilali Mohammet (sometimes referred to as Bu Allah). Bilali was an African Muslim born in
Timbo Guinea between 1760 and 1779. Accounts differ about when Bilali was taken from Africa to the Americas, but Spalding seems to have purchased him about 1802. During the
War of 1812, Spalding placed Bilali in charge of training other slaves with muskets to aid in the defense of Sapelo Island in the event of a British invasion. At some point during his enslavement on Sapelo Island, Bilali wrote what is now referred to as the
Bilali Document, a manuscript on West African Islamic law written in Arabic. ==Later life==