The Louisiana Purchase marked the beginning of a new era in the history of the United States. Land that had known only Indian inhabitants had the drawing power of a magnet and civilization again started its steady creeping westward.
In the early Nineteenth century the Sioux Indians along with the Sacs and Fox were the main inhabitants of this great land, along with a few transient fur traders. In 1803 the territory was purchased by the United States from France; and so it was that in 1804 the United Army sent Captains Lewis and Clark exploring up the Missouri River on their way to the Pacific Coast. During the course of this trip Sergeant Charles Floyd took sick and died and was buried on a high bluff south of a stream they named the Floyd River. The grave was marked with a cedar post which stood there for many years. By 1856 spring's freshet wiped out the last hundred feet between river and grave. The skeleton lay exposed somewhat more than one hundred feet above the water. The remains were rescued and re-interred about two hundred feet farther from the river. The Floyd Monument was erected on that spot in 1895.
The territory along the eastern shore of the Missouri River was ceded by the Sioux, Sac and Fox Indians on July 15, 1830, and settlers began to flock into the Iowa Territory. In 1839, steamboat "Antelope" for the upper Missouri region where they engaged in trade for the American Fur Company. Many of these men later returned to Sergeant Bluff with their families to settle.
William Thompson with two other men settled south of the Floyd Monument in the summer of 1848. A town was laid out and named Thompsontown. One large cabin was built at this site. Others following preferred a location a couple of miles farther south and this settlement was known as Floyd's Bluff. This early town in 1850 was inhabited mostly by trappers, traders, and hunters who dealt in trade among the Indians.
On January 15, 1851, the Iowa Legislature created the boundary lines of the forth-nine new counties in western Iowa. One of these was Wahkaw, an Indian name, and it included all of northwest Iowa. From it have since been made ten other counties. During this same term of the legislature, Wahkaw County was renamed Woodbury, in honor of the Hon. Levi Woodbury, an eminent man of his time who had served on the Supreme Court bench. An act was passed appointing three commissioners to locate the county seat near its center and to organize the county Woodbury. The Commissioners were further instructed to name the selected site Sergeant's Bluff. Thompson's plat of Floyd's Bluff was chosen. Thus the village of Sergeant Bluff was started in 1852, a year after the organization of the county. Under the name of Sergeant's Bluff City it was registered as the first formally platted town in Woodbury County, on November 20, 1854. Thus Woodbury County and Sergeant's Bluff were organized before Sioux City was even thought of.
The town has been known by several names. Thompson called it Floyd's Bluff. The residents themselves preferred the name Woodbury, and indeed, most deeds and titles to lots in the town will show that it was registered with the land offices as Woodbury, and that its first mail came under that address. However, the state legislature had passed a law decreeing that the town be called Sergeant's Bluff, and so the residents were forced to agree but only after the Dun Shipper's Guide and the federal post office had both listed it as Sergeant Bluff.
The town's name appears on all early records and plats with a final "s" to both words Sergeant and Bluff, but local residents dropped the "s" from Bluffs. The post office recorded it with no final "s" and so it is legally known now as Sergeant Bluff.