Among the ambitious state-of-the-art designs of the late steam era, Alco's Challengers, Big Boys, and high-speed streamliners stood out for their success in operations.

2626 and ran it on the North Coast Limited, as well as its pool trains between Seattle, Washington, and Portland, Oregon, and excursions, through 1957.

The building was converted to make diesel locomotives to compete with those of the Electro-Motive Division of General Motors.

[9] Joseph Burroughs Ennis (1879–1955) was a senior vice president between 1917 and 1947 and was responsible for the design of many of the company's locomotives.

An Alco racing car won the Vanderbilt Cup in both 1909 and 1910 and competed in the first Indianapolis 500 in 1911, driven on all three occasions by Harry Grant.

[10] The Alco automobile story is notable chiefly as a step in the automotive career of Walter P. Chrysler, who worked as the plant manager.

It built additional locomotives for the Long Island Rail Road and the Chicago and North Western Railway.

In 1939, ALCo started producing passenger diesel locomotives to compete with General Motors' Electro-Motive Corporation.

The following year, ALCo teamed up with General Electric (Alco-GE) for much-needed support in competing with EMC.

The versatile road–switcher design gained favor for short-haul applications, which would provide ALCo a secure market niche through the 1940s.

The entry of the United States into World War II froze ALCo's development of road diesel locomotives.

During that time, ALCo was allocated the construction of diesel switching locomotives, their new road–switcher locomotives, a small quantity of ALCO DL-109 dual-service engines and its proven steam designs, while EMD (formerly EMC) was allocated the construction of mainline road freight diesels (the production of straight passenger-service engines was prohibited by the War Production Board).

[13] Alco's RS-1 road switcher was selected by the United States Army for a vital task: rejuvenating the Trans-Iranian Railway and extending it to the Soviet Union.

Not only was the company prevented from selling these locomotives to mainline U.S. railroads, but the 13 RS-1s that had already been built were commandeered for Iranian duty and converted to RSD-1s.

[9] The postwar era saw ALCo's steam products fall out of favor while it struggled to develop mainline diesel locomotives competitive with EMD's E and F series road locomotives, which were well-positioned from GM-EMC's large development efforts of the 1930s and its established service infrastructure.

Much of its success in this period can be tied to its pioneering RS locomotives, representing the first modern road–switcher, a configuration which has long-outlasted ALCo.

In 1956, ALCo made long-overdue changes, modernizing its production process and introducing road locomotives with its new 251 engine.

Despite continual innovation in its designs (the first AC/DC transmission among others), ALCo gradually succumbed to its competition, in which its former ally, General Electric, was an important element.

The vast ALCo Schenectady plant was completely demolished by 2019, and its site is now occupied by a large industrial park.

After the Korean War, Alco began making oil production equipment and heat exchangers for nuclear plants.

The business was subsequently sold to the Fairbanks-Morse corporation, which continues to manufacture Alco-designed engines in addition to their own design.

In January 1983, certain assets of the Alco Products Division of Smithco, namely double-pipe and hairpin-type heat exchanger products sold under the "Alco Twin" name, mark and style, were sold in an asset sale by Smithco to Bos-Hatten, a subsidiary of Nitram Energy.

In 2008, Nitram was acquired by Peerless Manufacturing Co[22] In 2015, Peerless sold its heat exchanger business to Koch Heat Transfer Co.[23] After the closure of Alco's Schenectady works, locomotives to Alco designs continued to be manufactured in Canada by Montreal Locomotive Works and in Australia by AE Goodwin.

The Diesel Loco Modernisation Works (DMW) at Patiala, India, do mid-life rebuilding and upgrading the power of these locomotives, typically the 2,600 horsepower (1.94 MW) WDM-2 to 3,100 horsepower (2.31 MW).A number of Alco and MLW diesel–electric locomotives (models DL500C, DL532B, DL537, DL543, MX627 and MX636) are in daily use hauling freight trains of the Hellenic Railways Organisation (OSE) in Greece.

Another fleet of Alco Bombardier locomotives run in rugged terrain on the Sri Lanka railway network.

[citation needed] In Portugal an Alco 2-8-2 built in 1945 (construction number 73480) is displayed at the National Railway Museum at Entroncamento.

[32] In February 2014, in the episode The Locomotive Manipulation of the TV series The Big Bang Theory, takes place on a train pulled by what is described as an "Alco FA-4".

Hired in 1946 as Alco's new company artist, Fogg began painting locomotives in the livery of prospective customers and taking photographs of them.

At an Alco gala at the Waldorf Astoria Hotel, Lucius Beebe, a noted journalist with the New York Herald-Tribune, sought out Fogg.

With commissions from individuals, authors, publishers, railroads, and related industrial firms flourishing, in 1957 Fogg ended his formal agreement with Alco.