Scroll over the map below for details on each state's primary or caucus. Click each state to see which candidates won. Note that for the handful of states with Democratic and Republican contests on different days, the color key corresponds to the date of the first contest.
Quick civics lesson:
The number of delegates up for grabs in each state generally reflects its population size. In most states, delegates are allocated proportionately based on the results of the primary or caucus (although in a handful of Republican contests, including Florida and Delaware, the Republican primary is winner-take-all).
This means, unless the race remains incredibly close into the late spring -- which was a possibility this year --each party's nomination is generally secured long before a decent number of states get to vote. The staggered nature of this system affords candidates the luxury of focusing resources on specific areas of the country rather than trying to be everywhere at once.
However, the system is also somewhat controversial, in that millions of voters in late-primary states -- including California -- often miss out on the opportunity to directly impact the outcome of their party's nomination. Opponents of the process argue that this gives undue influence to small, largely white, rural early-voting states like Iowa and New Hampshire, which they say, can result in nominees who don't necessarily represent the preferences of the larger U.S. electorate.
Note that most delegates are "pledged," meaning they are mandated to support a particular candidate at their party's national convention in July. However, each party also has a certain number of unpledged delegates, and these guys can support whoever they want. In the Republican Party they're called "unbound delegates" and make up about 7 percent of the total delegate count. In the Democratic Party, they're known as "superdelegates" and make up 15 percent of the delegate count. As mentioned earlier, Clinton is ahead of Sanders in the pledged delegate count. But what makes her overall lead so formidable is the overwhelming portion of party superdelegates, who have committed to supporting her (a process that Sanders and his supporters call blatantly unfair).
Last technical thing to keep in mind (for now) in this incredibly complicated process: a primary or caucus is considered "closed" when participation is limited to only registered members of that party, "open" when participation is open to all registered voters and "mixed" when independent voters are allowed to participate.