Hillary Clinton is the presumptive Democratic Party Presidential candidate according to reports by the Associated Press who put together a tally of Democratic Party delegates who voted for Clinton last night. The count puts Mrs Clinton on 2,383 - the number needed to make her the presumptive nominee which makes her the first female nominee for a major US political party.
But her main rival for the party's ticket, Bernie Sanders, says she hasn't won as her candidacy is dependent on super delegates who can't vote till July.
'Superdelegates' are party insiders who can pledge their support for a candidate ahead of the convention but do not formally vote for them until the convention itself.
According to AP, Mrs Clinton, on Monday night, reached the threshold with a big win in Puerto Rico and a burst of last-minute support from superdelegates.
At an appearance in Long Beach, California, shortly after the news broke, she said: "We are on the brink of a historic and unprecedented moment but we still have work to do.
"We have six elections tomorrow and we're going to fight hard for every single vote, especially right here in California."