Sergeant John Ordway (c. 1775 – c. 1817), the youngest of ten siblings, was an important part of the Lewis and Clark Expedition across the United States.

John Ordway was one of the sergeants from the United States Army who stepped forward to volunteer for the Corps of Discovery.

Ordway exercised many responsibilities on the trip, such as issuing the provisions, appointing guard duties, and keeping the registers and records.

Before the journey, John Ordway sent a message to his parents telling them of the purpose and determination of the expedition: We are to ascend the Missouri River with a boat as far as it is navigable and then go by land, to the western ocean, if nothing prevents, &c. This party consists of 25 picked Men of the army & country and I am So happy as to be one of the, pick'd Men...We are to start in ten days up the Missouri River...We expect to be gone 18 months or two years...If we make Great Discoveries as we expect, the united States, has promised to make us Great Rewards more than we are promised, &c."[2]In February 1804, during the staging of the journey and still at Camp Dubois (also known as Camp Wood), Illinois, while Lewis and Clark were away and Ordway was in charge, some of the men became drunk while they were on their guard duty.

John Ordway returned from the Lewis and Clark Expedition and married Gracey Walker and became a successful landowner in what became New Madrid County, Missouri.