In 1895, W.C. Zimmerman founded the Monarch Grubber Company in Lone Tree in partnership with Miles Bateman. In 1908 it became the Zimmerman Steel Company. Originally, they bought parts for assembly at the plant, but in 1897 they began casting their own parts in a new building just south of the railroad tracks. This was the first steel casting plant in Iowa. In 1898 W.C. took Henry, his eldest son, into the business with him and he sent his daughter, Bertha, to Iowa City to the Irish Business College. The next year, at the age of thirteen, Bertha took over the business correspondence for the company. Eventually all of W.C.'s sons would come into the business. In September 1906 the Zimmermans contracted for the electric franchise for Lone Tree. According to Henry Zimmerman, within three months, under the direction of his brother Fred, Lone Tree had electric lights. In 1911 the Zimmerman Steel Company shipped steel products to twenty countries including Russia, Japan, and Australia. At its peak the factory employed fifty people in what were considered high-paying jobs. The family also owned a farm, which was near the large elm tree from which the town derived its name.

Henry L. Zimmerman was born in Davenport on July 25, 1879 and attended schools in Big Rock and Lone Tree, Iowa. According to a memoir in the collection, a study of his father's books one Christmas holiday convinced him that he was needed at the company. He talked his father into hiring Andrew Hess, who Henry described as "the most skillful steel moulder in the Upper Mississippi Valley." After serving an intense apprenticeship under Hess, he took control of his father's plant. This memoir also states that he performed the town's (presumably Lone Tree's) civil engineering for seven years and during that time is said to have brought telelphone service to the community, to have taken on the completion of the community waterworks when an out-of-town contractor failed to complete it, and to have redesigned the town's wells. In addition he designed all the equipment for the steel works, except the electrical motors.

In 1915, Henry designed the Zimmerman Steel Company east of Bettendorf, Iowa and became Vice-President in charge of buying and shipping. He also began taking classes in business and engineering. In 1929 The Santa Fe Railway acquired many steel companies and they hired Henry as foundry engineer in which capacity he travelled from the Mississippi to the eastern seaboard inspecting the plants, taking care of problems and working to make them more efficient and productive.

In the early nineteen thirties Freyn Engineering Company selected Henry as their chief foundry engineer, one of fifty- seven specialists chosen to establish modern steel mills in Russia. He arrived at Kuznetz, Sibera on January 7, 1931. The temperature was 81 degrees below zero. The hotel where he was staying had no heat because the steam heaters installed by German workers had frozen and burst their pipes. The temperature inside the hotel was sixty-six degrees below zero. On the job, they poured concrete at thiry-five below and kept it warm with hot stones and boiling water. The plant at Kuznetz went into production sixty days ahead of schedule, well before the 286 other plants scheduled to open at the same time. The Russians were so impressed that they made a film of him at work.

While there, he revised some engineering American textbooks which had been translated into Russian.

One of his projects was to remodel a metallurgical works in a building built in 1794. Eventually, Russia ran out of money and the projects were terminated. When Kruschev visited Iowa in the nineteen-sixties, Henry met him and met with his technical advisers, who told him that the plant he had built in the thirties was still working fine.

After returning from Russia, he did consulting work, repairing existing plants and building new ones. During World War II he served as chief inspector for the Bureau of Ships as a civilian through General Motors' Electromotive Division. In his memoir in the collection, Henry rather cryptically states that the family "lost control of the Plant on War contracts."

In his later years, he worked on a design for a rotary engine and lived in Davenport with his daughter and son-in-law, C.H. Wildman, the sheriff of Scott County. At one point, he ran for the House of Representatives in the First Iowa Congressional District on the Democratic ticket. Henry L. Zimmerman died in April 1971.