Northern States Power Company (Minnesota) (NSP) was a Minneapolis-based, publicly held energy company. (After about 2000 it was known as Xcel Energy.) It generated, transmitted, and distributed electrical power and natural gas to customers in Minnesota and in North and South Dakota. A related company, Northern States Power Company (Wisconsin), served customers in Wisconsin and in Upper Peninsula Michigan. Northern States Power Company had its beginnings as the Washington County Light and Power Company (Stillwater, Minn.), organized in June 1909 by entrepreneur Henry Marison Byllesby (ca.1859-1924). Byllesby was at one time a draftsman for inventor Thomas Alva Edison. The company's name was changed later that year to Consumers Power Company, and in 1916 to Northern States Power Company. Byllesby's strategy was to purchase, rehabilitate, and build public utility properties. The company grew steadily through a series of mergers and acquisitions (including 42 companies in just 7 years during the 1920s) under Byllesby's leadership. Some of these firms date back to the 1850s.

The Minneapolis Mill Company and the St. Anthony Falls Water Power Company, which figure largely in this collection, were formed by the various owners of water power rights at the Falls of St. Anthony in order to equitably apportion the river water available to the mills and other users at the falls. Both were chartered in 1856 and, while separate corporate entities, they were for most of their existence jointly operated by the same management. These firms leased water for power to the various users in units known as "mill powers." A mill power was the quantity of water required to develop about 75 theoretical horsepower. Mill powers were leased to the users at annual rentals ranging from $100 to $1500 per mill power.

The St. Anthony Falls Water Power Company, based on the east bank of the Mississippi River, was incorporated in 1856, although it had been operating informally for a few years prior to that. Incorporators included Franklin Steele, Thomas E. Davis, John F. A. Sanford, Frederick C. Gebhard, Richard Chute, and John S. Prince. It received its charter from the Minnesota Territorial Legislature on February 26, 1856. The company controlled the water power on the east side of the Mississippi River at the Falls of St. Anthony. The east bank land was at that time owned by Steele, Davis, Sanford, and Gebhard. Chute of Minneapolis and John S. Prince of St. Paul purchased a one-eighth interest in the property from Steele. Chute's interest in the company eventually grew much larger, and by 1875 he and his brother Samuel held a one-half interest in the company. Between 1868 and 1880 a dam was built, sawmills erected, flumes excavated, and mills and factories located on the east bank of the river. The Chute brothers sold the stock of the St. Anthony Falls Water Power Company to James J. Hill and his Great Northern Railway Company associates in 1880. Hill managed and controlled the company until it was merged into the Pillsbury-Washburn Flour Mills Company in 1889. The company was granted an electrical franchise by the city of Minneapolis in August 1896 to engage in the electric utility business. In 1895 it began to construct a Lower Dam and hydroelectric power generating station, which was leased by the Twin City Rapid Transit Company to help power its street car lines. Electric power was first generated in this plant on November 12, 1897. In 1908 the company completed its new Hennepin Island Plant, another hydroelectric facility leased by the Twin City Rapid Transit Company.

The Minneapolis Mill Company, based on the west bank of the river, was chartered by the Minnesota Territorial Legislature on February 27, 1856. Incorporators included Robert Smith (president), George E. Huy (secretary), D. Morrision (treasurer), Roswell P. Russell, M. S. Olds, and Jacob Elliott. The company constructed a log dam from the west bank of the Mississippi eastward to meet the dam of the St. Anthony Falls Water Power Company in 1956-1857. Most of the flour mills and saw mills along the west bank took water from a canal built in 1857-1865 (deepened in 1885), discharging it back into the river through tunnels and tail races below.

Pillsbury-Washburn Flour Mills Company, Ltd., was formed in the Fall of 1889 and became the property of a London syndicate. The syndicate also purchased the St. Anthony Falls Water Power Company and the Minneapolis Mill Company, and operated them as separate companies under one management. Pillsbury-Washburn went into bankruptcy in 1908 and, following a long receivership, its assets were acquired by the Pillsbury Flour Mills Company in 1923. These assets included the two water power companies. On December 23, 1923 the water power companies were both sold by Pillsbury to Northern States Securities Corporation, a subsidiary of Northern States Power Company. Northern States Securities was dissolved in 1937, and the two water power companies became direct subsidiaries of Northern States Power Company (Minnesota).

Most of the information on the water power companies was taken from Herbert W. Meyer, History of St. Anthony Falls Water Power Co. and Minneapolis Mill Co. .