Born in March 1853, at Humboldt Bay, in California, he was the son of U.S. Army Lieutenant Edmund Underwood and Mary Moore Beardsley.
He founded a monthly newspaper, O Le Faatonu, which was distributed freely for fifty years, providing news about government activities and global events.
Together with Governor Wilhelm Solf of Western Samoa, Underwood attempted to address this problem through potential land exchanges and compensation, but they were unable to reach a resolution.
During his visit, he discovered that the Tuimanua might agree to cede the Manuʻa Islands to the United States if the U.S. Navy would construct schools there.
The idea of Native indolence, prevalent at the time, portrayed Samoans, like other colonized peoples, as lazy, unreliable, and inconstant workers who were unsuitable for complex or long-term labor projects.