The Horse Collar
1851
The development of a better horse collar meant that more land could be plowed, more crops could be grown, and there was extra food to trade with other people. It also meant that not everyone had to grow their own food. It meant that people who were not farming were free to build towns and farmers could supply the food while other people could develop new trades. As people took on new jobs, they discovered that the horse could also be used to help with these new tasks. The towns grew into cities. The horse was an important power source through the 19th century and even into the 20th century with the collar style from the year 1000 still in use.

Illustration from:
The Journal of the Royal Agricultural Society of England, v. XXII, 1851; "XXVII. Report to H.R.H. the President of the Commission for the Exhibition of the Works of Industry of all Nations. On Agricultural Implements, Class IX," by Ph. Pusey.