[3] Neumann was the Republican Party of California's candidate for the United States House of Representatives in November 1882 for the San Francisco district.

In 1883, Neumann came to the Hawaiian Islands to serve as legal counsel for Spreckels who was now the publisher of the Honolulu Advertiser newspaper, first in the fall for a short visit.

Within days of returning, Neumann was admitted to the bar and appointed as attorney general of the Kingdom of Hawaii, and a member of Kalākaua's Privy Council on December 14, 1883.

Neumann was sometimes attacked by the conservative press for his "bohemianism", including playing Poker with the king, which the missionaries thought was sinful.

[4] He had been president of the Bohemian Club in San Francisco[9] Charles T. Gulick, although related to missionaries, also became a member of the Kalākaua cabinet as Minister of the Interior.

[11] He defended Liliʻuokalani and other prisoners in a military tribunal following the failed 1895 rebellion against the Republic of Hawaii, where she was convicted of misprision of treason.

[15] Although he had no government position, he was accepted in society enough to become toastmaster of the local Masonic Lodge,[16] and president of the Hawaii Bar Association.

[20] Son Edouard Neumann graduated from the United States Naval Academy (nominated by California congressman Julius Kahn),[6] but was killed in a fire during target practice on the USS Missouri on April 13, 1904.