How the Victorians Wired the World is a fascinating documentary of the telegraph's influence on modern life. Though it was made in 2000, near the height of the dot-com bubble, its message is no less profound today.
I think connective technologies are the most powerful influencers of human behavior today. To understand ourselves, we must understand the elemental nature of that which owns our attention. The internet and mobile devices are our masters today, but in many ways, they are far more evolutionary than revolutionary on the grander time scale of technological development.
Before the internet, we had forms of instant communication unconstrained by distance. Before the telegraph, we did not.