The principals of this partnership, Osterheld & Eickemeyer, were George Osterheld and Rudolf E. Eickemeyer. They are known to have been in business 1864 until 1892, and they were possibly in business earlier than that as well. They manufactured patented hat-making machinery, a steam-engine governor, and they also made an unusual copy lathe that used 4 rat-tail cutters; this lathe was intended for making hat molds.

By the late 1880s, Osterheld seems to have been inactive in the company, although his name still appeared over the door. Eickemeyer's son, Rudolf Jr., is listed as co-signer of papers incorporating related businesses. Rudolf Jr. later became well known in his own right, as a photographer.

Eickemeyer was interested in the burgeoning field of electricity. Electric lighting was beginning to appear on city streets and in the residences of the wealthy. Electric motors appeared to hold promise in replacing steam engines in powering industry, and in powering motor vehicles, especially streetcars. In 1889 Osterheld & Eickemeyer started to manufacture DC electric motors designed by Eickemeyer. Soon after, a new immigrant from Germany, one Charles Proteus Steinmetz, interviewed for a position with the company. Eickemeyer and Steinmetz hit it off, each recognizing the ingenuity of the other. Steinmetz was hired as a draftsman but soon started working closely with Eickemeyer on AC motors. During this time Steinmetz developed his famous "law of hysteresis" to explain why AC motors and transformers did not follow Ohm's Law. This was an important development that gained Steinmetz much attention and admiration in the industry. The AC motor developed and patented by Eickemeyer and Steinmetz would prove to only work well at frequencies lower than those typically used at the time so it was ultimately not successful. Nonetheless, the firm of Osterheld & Eickemeyer was seen as an important innovator, and Steinmetz was recognized as one of the preëminent electrical engineers in this early era of electricity and electric motors.

In 1892 the business of Osterheld & Eickemeyer was acquired by General Electric Co., part of an industry consolidation into just two firms, GE and Westinghouse. Eickemeyer died just a few years later, in 1896.

Steinmetz, meanwhile, stayed on with GE and soon proved himself to be an invaluable asset for his detailed understanding of how to develop AC devices, and he also proved to be an excellent communicator who taught the other GE designers how to use his techniques to design motors, generators and transformers. Steinmetz developed the use of complex-number phasor notation that is still widely used by electrical engineers today. He also systematized the analysis of passive AC circuits (those with resisters, inductors and capacitors). He died in 1923, age 58, due to complications from a hereditary spinal deformity that caused dwarfism, a hunchback and hip dysplasia, and whose symptoms worsened over the course of his life.

Information Sources

• 1864 Directory of Westchester County lists this firm as machinists in Yonkers, with an address of "Chicken Island".
• 1870 and 1872 issues of Boyd's Business Directory of New York State lists this firm as "machinists".
• 1867-05-11 Scientific American features an article on "Eickemeyer's improved governor for marine and stationary engines", and mentions that it is manufactured by Osterheld & Eickemeyer.
• Wikipedia biography of Charles Proteus Steinmetz.
• YouTube video biography of Charles Steinmetz describes Steinmetz's work at Osterheld & Eickemeyer and his subsequent work at GE.