John Andrew Rea arrived across the river in Bismarck in 1876 to serve as temporary editor of its newspaper during one of its founder's extended absences.

Rea subsequently served as the register in the governmental land office in the territorial capital of Bismarck for eight years starting in June 1880.

Rea claimed he and Northern Pacific Railroad engineer Thomas L. Rosser created the name.

Gerard had married Helena Catherine, an Arikara/Ree woman when he ran the Fort Berthold trading post.

Gerard was appointed by the Dakota Territorial governor as Morton County's first assessor when it was established in March 1878.

[13] While Native Americans had long established settlements in the area along the river, the first white explorer was Frenchman Sieure de la Verendyre, whose expedition arrived in 1738.

Not until the early 1800s did Euro-American frontiersmen come to the area with any regularity, the Lewis and Clark Expedition in 1804 and 1806, George Catlin in 1832, and Prince Maximilian and Karl Bodmer in 1834 being the most notable.

In 1830 the American Fur Company established the Fort Clark Trading Post 40 miles upstream on the Missouri River to support trappers.

To provide protection for the approaching rail line from the east and the homesteaders who would surely follow, the US Army established two outposts in the area in 1872 and 1873.

On the west side, an infantry post, Fort McKeen, was constructed on bluffs above the confluence of Heart and Missouri Rivers.

In 1873 Congress authorized the addition of a cavalry post and changed its designation to Fort Abraham Lincoln when foot soldiers were deemed ineffective against their mounted adversaries.

Once its final location was announced, about five miles north of Fort Abraham Lincoln, a work camp appeared on the west riverbank in December 1878, complete with its own post office.

[14] The City of Mandan was formally incorporated on February 24, 1881, and was named for the Mantani Indians, or "people of the bank."

Upon completion of the railroad to Montana in 1881, Fort Abraham Lincoln had fulfilled its primary purpose and gradually declined until it was formally abandoned in 1891.

Historical records indicate it served steamboat traffic as early as 1832 when the riverboat Yellowstone reached Fort Union.

The Army Corps of Engineers made extensive riverside improvements, including adding dry-dock and boat repair facilities.

The top six ancestry groups in the city were German (61.3%), Norwegian (15.4%), Russian (13.1%), Irish (7.9%), English (4.2%), and Native American (3.02%).

The city continues to support the agricultural industry with livestock sale ring, farm implement dealers and suppliers and finance/lending institutions.

Subsequent access to rail transportation allowed the agricultural, commercial and industrial sectors to flourish.

In recent decades, Mandan has diversified its economy to include food processing, petroleum refining, electrical power generation, software development, manufacturing and retail trade as well as all manner of professional services for its residents.

In 2021, IDG Insider Pro and Computerworld Magazine honored NISC as one of the Top 100 "Best Places to Work in IT" for the 18th consecutive year for midsize organizations (companies with 1,001 to 4,999 employees).

NISC and its subsidiaries employ over 1,300 people with offices in Iowa, Missouri, North Dakota, and Virginia.

Over 450 of these employees work at NISC's Vern Dosch National Campus in Mandan, making it the city's second-largest employer.

Today, the Mandan Refinery's nameplate capacity of 73,800 BPD processes primarily North Dakota sweet (low sulfur) crude oil into a full range of refined petroleum products.

[31] In total 250 employees are based at the site, including the Andeavor Logistics LP group, which supports trucking and crude pipeline and natural gas transportation and processing operations.

Heskett, the founder of Montana-Dakota Utilities Co. As the seat of Morton County, all major governmental service offices are in Mandan, including the courthouse.

Operated by the State of North Dakota, the campus includes four cottages, administration and education facilities, a gymnasium with an indoor swimming pool, a chapel and a cafeteria.

Mandan was a scheduled meal stop for the Northern Pacific Railway east-west passenger line beginning in 1882.

In 2016, the Mandan Public School District was Morton County's largest employer, with approximately 700 employees.

Bismarck State College operates two campuses in Mandan focusing on post-secondary vocational education.