The Democratic Party caucuses in Guam have given Hillary Clinton almost 60 percent of their votes, completing a clean sweep of the three US Pacific territories in her bid for the US presidency.
In earlier primaries, she had secured more delegates than her rival Bernie Sanders in both the Northern Marianas and American Samoa.
In Guam, Mrs Clinton secured pledges of four delegates and Mr Sanders three, with five more delegates being considered as super delegates.
During the campaign, Mrs Sanders told the Guam media that her husband supported the efforts of Guamanians to hold a binding referendum on their desired political status.
Mrs Clinton's daughter said having visited Guam, her mother was also keenly aware of the island's importance to America's national security.
Last month, Guam's delegate to the US Congress, Madeleine Bordallo, who is also a Democrat, took exception to comments by a US actor and Sanders supporter, Tim Robbins.
He had described Mrs Clinton's win in the primary election in South Carolina as about 'as significant as winning Guam'.
Ms Bordallo said the Guamanians' lack of voting rights in US elections had been reduced to a political punchline.
The actor later apologised.