As the latest issue of BTJ is also devoted to the ro-ro & ferry market, whose players trade in trailers, it's maybe worth mentioning Alexander Winston who back in 1898 invented what's today know as a semi-trailer ("transport" in Canada; "semi" or "single" in Australia and New Zealand; "big rig" or "eighteen-wheeler" in the US; or "artic" in the UK and Ireland).
His company, the Winston Motor Carriage Company of Cleveland, manufactured cars. However, there was the issue of transporting them without wear and tear to their final customers, sometimes located hundreds of miles from Alexander's workshop. As such, Winston develop an attachable cart with a platform on which the car rested comfortably.
Nevertheless, the actual phrase "semi-trailer" was coined by August Charles Fruehauf, who in 1918 set up the Fruehauf Trailer Company. Just look at the design of the one they made for Pioneer Sugar, sleek!