Originally the area now known as Morton County became a part of the United States through the Louisiana Purchase in 1803. The area was part of the Louisiana Territory from 1803 to 1812, part of the Missouri Territory from 1812 to 1834, part of Nebraska Territory from 1834 to 1861, and became part of the Dakota Territory on February 26, 1861. The Dakota Territory was opened for settlement on January 1, 1863.

Morton County was named after Oliver Perry Morton, the Governor of Indiana, a man who actively supported the United States administration during the Civil War. Several attempts at organization were made before Morton County finally became successful in establishing a Permanent County setup. The County was actually founded in 1878 but in 1879 the Territorial Legislature annexed an 18-mile wide strip of Morton County (including Mandan) to Burleigh County, leaving the remainder of the County unorganized. Morton County was reunited and organized for the second time in 1881. The present boundaries of the County were established in 1916 after the splitting-off of Sioux County in 1914 and the creation of Grant County in 1916. The present land area of Morton County is 1,228,928 acres or 1920.2 square miles, not including water surface area. The county encompasses 15,232 acres or 23.9 square miles of water.

Evidence of inhabitation of the Morton County area dates back over 9,000 years. These original inhabitants were both nomadic and sedentary or agrarian people. Native American groups included member of what are now known as the Mandan, Hidatsa, Arikara, Lakota, and Assiniboine. Each of these groups depended on the Buffalo, particularly the Lakota and Assiniboine who were more nomadic. The Mandan, Arikara, and Hidatsa maintained a sedentary, agrarian lifestyle with regular hunting expeditions for buffalo and other wild game. A flourishing trade in furs, shell, and Knife River Flint by the Mandans and other native groups resulted in contacts with other cultures reaching out to both coasts of the North American continent.

The earliest record of non-Indian visitors to the Morton County area indicates a 1738 French expedition led by Louis Verendry visited the Mandan Indian villages near what is now the City of Mandan. Verendry was followed by MacKenzie who was seeking passage to the Pacific Ocean. Following MacKenzie, in 1804, the Lewis and Clark Expedition made their winter camp approximately 40 miles upstream of the current location of the City of Mandan near the current location of Washburn. The non-Indian visitors brought with them several infectious diseases such as smallpox which resulted in the deaths of thousands of native peoples who, having never been exposed, had not developed a resistance to the diseases. Trappers and fur traders followed the Lewis and Clark Expedition, and by the early 1860’s, military outposts began to spring up.

Fort Rice became the first permanent white settlement in Morton County in 1864 followed by Fort Lincoln and Fort McKeen. Fort Lincoln is where George Armstrong Custer and the 7^th Cavalry began their fateful march to the Little Bighorn in June of 1876.

Within five years after the Battle of the Little Bighorn, the Northern Pacific Railroad line was completed through the Morton County area. The NP Railroad built a train station at Mandan. Around the turn of the century a large wave of immigrant settlers and homesteaders began streaming into the County.

Mandan, located along the Missouri River in the northeastern corner of the County serves as the County Seat and is the largest urban area in the County. Mandan is the second oldest incorporated city in the state, having filed for incorporation on February 21, 1881. This second incorporation of a North Dakota city occurred six years after Fargo was incorporated.

Colonists from Ohio, Indiana, Wisconsin, Illinois and Minnesota settled Glen Ullin in May of 1883. The town name was derived from the Gaelic word, "Glen", meaning valley, and "Ullin" which comes from a favorite English ballad; "Lord Ullin’s Daughter". Glen Ullin was incorporated in 1910.

New Salem (originally just Salem) was renamed because a Salem already existed in the southern half of the Dakota Territory. New Salem, like Glen Ullin was settled in 1883 and later incorporated as a village in 1911.

Flasher was founded in 1902 and was incorporated as a village in 1914. It was named for Mabel Flasher, whose homestead is now a part of the townsite known as West Flasher.

Hebron (originally called Knife River) derived its name from a traveling minister who recommended the name change because the valley here reminded him of the Biblical vale of Hebron. Settlement began here in 1885 and the incorporation of the city came about in 1916.

Almont, the youngest of the incorporated communities in this report (incorporated in 1936), was named for the local buttes, the Altamont Moraine. Alta being Latin for high, Montis is Latin for mountain.

Although the simultaneous settlement of several other smaller communities in Morton County was occurring in the late 1800s and early 1900s, the following have not become incorporated municipalities: Breien, Ft. Rice, Huff, Judson, St. Anthony, and Sweet Briar.