This is a JavaScript implementation of an algoritm to construct continuous area cartograms, by James A. Dougenik, Nicholas R. Chrisman and Duane R. Niemeyer, ©1985 by the Association of American Geographers. It relies heavily on d3 for rendering and TopoJSON both for writing and reading topological JSON geodata.
The included example combines TopoJSON-encoded and boundaries of the United States from Natural Earth with 2011 US Census population estimates to size each state proportionally.
I include small modifications to how states and Washington DC are colored, which use a lookup table for the state of same-sex marriage laws in the United States as of May 19, 2014 (http://www.freedomtomarry.org/pages/where-state-laws-stand); updated most recently on June 6th, 2014 for Wisconsin.