What is this? This is an interactive map showing the legality of same-sex (gay) marriage and civil unions in the United States.
How can I find more information about a state? Click on the state to get a timeline of important events regarding same-sex marriage law.
What's a cartogram? A cartogram is a kind of map that shows states roughly in proportion to their population, and so it's more representative of how many people in the US are living under which laws. In this case, I based the cartogram on this Wikipedia cartogram of the 2008 election. Ideally the cartogram would change based on what year we're showing to keep up with population. Also note that small states are slightly overrepresented since every state gets at least 3 electoral votes.
What's the deal with Colorado? In the past, some states like Colorado and Nevada had civil unions, but marriage was against the constitution. I went with the green color instead of the dark red to emphasize that same-sex couples did have some rights, which seems more important than the fact that marriage was off limits.
How did you determine the difference between "Civil unions" and "Civil unions with some rights included in marriage"? I mostly relied on the determination made by the Human Rights Campaign - here's a PDF map of the states that currently recognize same-sex marriage and civil unions.