The modern knuckle coupler has its origins with the patent of Eli H. Janney granted on April 29, 1873. In 1877 he associated himself with the firm of McConway & Torley which produced and improved the coupler. Mr. Janney continued to patent improvements to the coupler as late as 1912 – the year of his death. In time the Master Car Builders Association adopted the term “vertical plane coupler” to identify it in a generic manner. But, the M.C.B. was reluctant to adopt a design whose mating face patent was controlled by one firm; in 1888 it reached an agreement with McConway & Torley that placed the mating face design in public domain. The Master Car Builders Association then adopted the design as the “M.C.B. Coupler.” During this period there were many other variants and improvements patented by others. By the end of 1899 the M.C.B. had approved forty-nine manufacturers of the “vertical plane coupler” that would work together.

The United States in 1893 enacted “Safety Appliance Act” and it became law on March 2, 1893. This provided for application of automatic couplers, automatic brakes and common locations of grab irons on railroad cars. The initial change over date was January 1, 1898, but this was extended to July 1, 1900. The railroads were opposed to the required changes and the costs of doing these.

The law stated, “On January 1, 1898, it will be unlawful for a common carrier used for interstate commerce to haul or permit to be hauled any car that is not equipped with couplers coupling automatically by impact and which can be uncoupled without a man going between the ends of the cars.”