When out fishing one day, we hiked way back into the forest. We found some very old power poles that had been stripped of their wire. Some were rotted away and several were still standing. On some were glass insulators. In reading about them I learned that the use of insulators began when the telegraph came out. The glass things were non-conducting of electricity and aided in moving the current. The initial ones were made in the 1860-1880s. The telephone insulators which were many colors, came out in the 1880s. When power lines started going underground in the 1960s, glass ones were no longer needed, and soon people started seriously collecting them. There are volumes written about glass insulators. Some can be worth thousands of dollars. I still have about a dozen of them from the early 1900s.
On that fishing trip we came home with more insulators than fish.