What were some of the major technological advances in agriculture that promoted the development of the western economy?1860-1900
There were a number of technological advances in agriculture after the Civil War that helped the economy of the western United States to develop.
I would say that one of these would be the invention of barbed wire. This allowed farmers to keep cattle from destroying their crops.
I would also point to the invention of various new kinds of plows. These started with John Deere's steel-faced plow and moldboard and went from there. There were also improvements made in hay mowers, reapers, manure spreaders, planters, and other kinds of farm equipment.
You also have to think of the railroads as a technological advance, I think. It was the spread of the railroads that really made the western economy viable.