The Leslie Corporation was started in the late 19th century by John Leslie, manufacturing steam-powered rotary snowplows for railroad use. Through the early 20th century, the Leslie company, located then in Lyndhurst, NJ, designed and manufactured all sorts of steam components, though the most recognized were their regulators and pressure valves. The company was by far not just a railroad supplier, and produced many steam-specific goods for both commercial and military ships throughout the first half of the 20th century. Over their lifetime, the company has grown, and has had two major relocations. First, in 1968, the company moved to Parsippany, NJ, to accommodate larger production facility needs. Today, they are located in Tampa, Florida and still produce many appliances for use in marine vessels, as well as railroad and industrial products. Some products include valves, controllers, regulators, hot water heaters, whistles, and more.

It wasn't until the 1930s that Leslie started producing air horns. Leslie bought the rights to the Tyfon series of horns, and eventually the SuperTyfon series, from Kockums in Sweden. One of the first horns that Leslie produced for railroad use was the Tyfon A-200, which was a great seller, being in production for over twenty years. It was known by many as the "GG1" horn, since the popular GG1s were fitted with pairs of these, which they carried throughout their service lives. The A-200, probably the most popular of the Tyfon air horns, found its way onto nearly every make and model of diesel or electric engine up until about 1950. It was about this time that Airchime had released their first chime horns into the railroad market.

Eager to jump on the bandwagon, Leslie made a short run with "Chime-Tone" horns, which were basically several Tyfons on a common bracket. Only a year or two later, Leslie unveiled a series of SuperTyfon chime horns that replaced the early Tyfon horns (which were single-note "honkers" with the exception of the "Chime-Tones"). With the introduction of the SuperTyfon series, Leslie was the first to have a "modern" chime horn (even before the Airchime P series). It had interchangeable parts among all power chambers, as well as a back caps that didn't screw into the head (unlike the Airchime M series). These two qualities have become the standard (as evidenced in Airchime P and K horns). It has worked so well for Leslie that they have kept their design almost unchanged since their first SuperTyfon. (WABCO had this concept down long before the SuperTyfon series, but never sold nearly as many horns as Leslie, in part due to marketing. In addition, WABCO only went as far as to build a two-tone horn utilizing these concepts.)

Though rumored to have left the horn business, this is not the case, though no railroads are known to have purchased any in recent years. Unfortunately, they seem to have priced themselves out of the market. I would assume that they do enough business to marine and industrial customers still. The Leslie company is now known as Leslie Controls, Inc. Below is a general timeline covering the major milestones in Leslie's horn lines.

Timeline

1934 - Leslie starts marketing its Tyfon series of air horns for railroad use
1950 - Chime-tone horns are introduced, giving Leslie the ability to market chime air horns.
1951 - Leslie SuperTyfon series is introduced with the S-5A, S-5D, S-3E, and S-3J. Chime-tone horns are dropped from the offerings.
1952 - SuperTyfon models S-5A, S-5D, S-3E, and S-3J are dropped in favor of the S-5T and S-3L, which have remained mainstays ever since.
1957 - Bronze power chamber construction was abandoned in favor of aluminum construction.
1966 - Tab-back power chambers dropped in favor of dome-back power chambers.
1968 - Leslie company moves to Parsippany, NJ.
1977 - Dome-back power chambers dropped in favor of the newer, RS-style, spike-backed power chambers.
1986 - Leslie company moves to Tampa, FL.