With the 4th of July weekend about to begin, the US Energy Information Administration decided to look back to our nation's founding. So it plotted the country's energy use starting from 1776. Most of the result isn't a surprise: biomass had a long run before fossil fuels took over and stayed on top. But recent years have seen the biggest change since nuclear was added to the mix.

Biomass spent nearly a century on top of the US energy mix before being displaced by coal, although it never went above providing four quadrillion Btus (each Btu is a bit over 1,000 Joules). But biomass never entirely went away, and its resurgence this century puts it at its highest level ever. With nuclear holding steady and renewables surging to nearly the same level as hydropower, fossil fuels are on the verge of dropping below 80 percent of the US' energy mix.

Fossil fuels haven't been that low a percentage for over a century.

Biomass' comeback is mirrored by the decline of coal. Coal was the US' dominant form of energy for roughly 75 years, until the rise of automobiles allowed petroleum to displace it. It saw another surge as the electric grid expanded starting in the 1960s, and coal's percentage of the mix continued to grow even as nuclear power expanded dramatically. But in the last few years, coal has dropped dramatically, in part due to a huge rise in the use of natural gas.

The EIA also includes projections out to 2040, but these tend to be of limited utility, as they assume no additional energy policies will be enacted. They also tend to miss rapid changes, such as the plunge in photovoltaic panel prices. Nevertheless, the projections suggest that use of fossil fuels will dip below 80 percent before this decade is out.