[3] Following this loss, Allen ran for the Maine Legislature once more, serving one term before moving from Bangor to Boston in 1847 and being elected to the Massachusetts House of Representatives in 1849.

He realized the potential for the Hawaiian Islands to provide agricultural products to the growing number of people in the California Gold Rush and tried to negotiate a trade treaty but failed.

[4] When he was replaced by an appointment from the Democratic Party president Franklin Pierce in August 1853, he decided to stay due to the severe shortage of legal professionals, and became a citizen of the Kingdom of Hawaii.

Within weeks he was appointed Minister of Finance for King Kamehameha III replacing Gerrit P. Judd, and from 1854 to 1856 served in the House of Nobles.

The newly married couple returned to Honolulu, where from June 1857 through February 1877, Allen was chief justice of the Kingdom of Hawaii Supreme Court.

[5] The Allens' first-born son, Frederick, was born ten days after Prince Albert Edward Kauikeaouli Kaleiopapa, and the two children became playmates.

In 1867, he bought a sugarcane plantation in an area called Princeville, Hawaii after the young Prince brought up with his son.

He left his son William Fessenden Allen from his first marriage in charge of the plantation, and went to Washington, D.C. to work out details of the trade agreement.