Hawaii was officially annexed to the United States through the Newlands Resolution, passed on July 4, 1898 as a joint resolution of Congress and signed by President McKinley on July 7. The Resolution also provided that “[t]he President shall appoint five commissioners, at least two of whom shall be residents of the Hawaiian Islands, who shall, as soon as reasonably practicable, recommend to Congress such legislation concerning the Hawaiian Islands as they shall deem necessary or proper.” The commissioners were to be named “by and with the advice and consent of the Senate.”
Congress adjourned for nearly five months the day after McKinley signed the Newlands Resolution. Rather than wait until December to choose his commissioners—Congress needed the recommendations “as soon as reasonably practicable,” after all—McKinley immediately empowered Sanford Dole (President of the Republic and then the Territory of Hawaii) and four others in accordance with the Constitution’s Recess Appointments Clause. McKinley duly submitted his commissioners’ names to the Senate on December 6, 1898, the day after it reconvened.
The Commission’s recommendations ultimately resulted in the Hawaiian Organic Act of 1900, which provided for limited territorial self-government. I learned in prior research that the Act also conferred American citizenship on all who were citizens of the Republic of Hawaii on August 12, 1898, the date of the ceasefire agreement that ended the Spanish-American War. Why Congress (or the commissioners) chose August 12 and not July 7 as the relevant date baffles me—Hawaiian annexation predated and bore no direct legal relation to the continuation or cessation of hostilities with Spain.