First mechanical excavator

The first land-based mobile excavator was the Otis Excavator, first built in 1835 by 22-year-old inventor William Otis (a cousin of elevator innovator Elisha Otis) in Canton, Massachusetts, USA. This prototype was tested in the construction of a railroad between Norwich, Connecticut, and Worcester, Massachusetts, in 1836.

Large-scale excavation machinery had been in use since the 17th century, and steam power had been in common use for this purpose for almost a century by 1835. All these previous examples had been designed for work in water, either dredging rivers and harbours, or else constructing dams and levees. The technology of the time was too heavy for a land-based carriage, and most trade was handled by ship or canal boat anyway.

For land-based projects, including early 19th century railroads, most earth-moving work was done by manual laborers (or "navvies"). A reasonably strong adult working at a sustainable pace can excavate about one cubic metre of earth in around four hours of digging with a shovel. Experienced and strong workers, like navvies, could manage as much as ten times that amount in the same time frame. The Otis Patent Excavator could reportedly move as much earth in a day as 40 or 50 navvies.

The initial prototype used a crane-arm with an iron bucket that was operated by means of an extending rigid arm and a system of chains and pulleys. It was all mounted to a heavy wooden carriage, which also supported the steam engine that powered the whole thing. Only the shovelling action of the bucket was steam-powered, however -- the 180-degree swing of the excavator arm was operated by men pulling on ropes, and the machine (which needed to be mounted on rails) had to be pulled by horses.

Not long after the excavator was completed, William Otis moved to Philadelphia, where he struck up a business partnership with Joseph Harrison, the factory manager at early locomotive makers Garrett & Eastwick - Harrison made a second, more advanced prototype which Otis patented in 1839.

Only seven Otis Patent Excavators had been built by the time of Otis' premature death from typhoid fever in 1839. Four were sent to Russia and one to the UK, while the other two were used on various civil engineering projects in the United States, including the landscaping for New York's Central Park and Boston's Back Bay Fens. The first of the Philadelphia-made excavators remained in operation until 1905, when it was reportedly scrapped in Canada.