A significant aspect of Caleb Cushing's long and distinguished career was his service as a US Commissioner to China in 1844 and the Treaty that was concluded through his negotiations over a 6 month period while in China.

Commercial expansion in Asia involved diplomatic entreaties with two important nations, China and Japan. The "China Market" was always a significant lure for American merchants who had engaged in trade with the empire since the 18th century. Following the conclusion of the First Opium War in 1842, Britain forced China to grant it special privileges, including exclusive British use of coastal ports. Not wanting to miss out on similar opportunities, President John Tyler appointed Caleb Cushing to undertake a mission to open Chinese ports to American trade. In 1844, Cushing negotiated the he Treaty of Wang Hiya (Wanghsia), the first treaty between the United States and China. This treaty granted to American merchants the same rights as Britain based upon the "most-favored nation" principle. The treaty with Japan would have to wait until the Perry Expedition in 1852-4. In a sense, Cushing and Perry occupied very similar roles. However, while Perry used force and the might of a US Naval squadron, Cushing employed persuasion and diplomacy without the resort to the clear threat of military force.

(Biography from the US Attorney General's Website)

Caleb Cushing
Twenty-Third Attorney General 1853-1857

Caleb Cushing was born in Salisbury, Massachusetts, on January 17, 1800. He entered Harvard at age 13, graduating in 1817. He studied law and was admitted to the bar in 1821. He was a member of the Massachusetts Legislature in 1825, and in 1826 a member of the State senate. Cushing was elected to Congress in 1834 and served until 1843. In 1843, as Commissioner to China, he made the first treaty between that country and the United States. He was elected again to the Massachusetts Legislature. In 1847, Cushing raised a regiment for the Mexican War, at his own expense. From 1850 to 1852, he was again in the Massachusetts Legislature, then was appointed associate justice of the Massachusetts Supreme Court.

On March 7, 1853, he was appointed Attorney General of the United States by President Pierce. From 1857 to 1859, Cushing served in the State legislature, and in 1860 President Buchanan sent him to Charleston as Confidential Commissioner to the Secessionists of South Carolina. In 1866, he served as one of three commissioners to revise and codify the laws of Congress. Cushing was sent to Bogota in 1868 to negotiate the right-of-way for ships across the Isthmus of Panama. In 1872 he was counsel for the United States at the Geneva Convention, and from 1874 to 1877 Minister to Spain, appointed by President Grant. He died in Newburysport, Massachusetts, on January 2, 1879.

Source: http://www.usdoj.gov/jmd/ls/agbiographies.htm#cushing