RAILROADS The most important change was whenever companies made a standard gauge because people needed to travel more distances faster and it was a lot of trouble reloading loads of resources.
INVENTION The most important change in inventions was when Alexander Graham Bell invented the telephone ,in 1877, because people could talk at a far away distance and have a two way conversation.
BUSINESS The most important change was when Edwin L. Drake struck oil in 1859 because oil was used as many things such as medicines, lubricated machines, and it could make smoke free light and heat.
LABOR The important change was when labor unions started fighting back for their wages in the early 1800's because that made more factories better and safer.