James Rockwell Sheffield (August 13, 1864—September 2, 1938) was an American attorney and Republican political figure who served in the New York State Assembly and was Ambassador to Mexico during the administration of Calvin Coolidge.
He was born in Dubuque, Iowa on August 14, 1864 and raised in Utica, New York. He attended Williston Seminary and graduated from Yale University in 1887, where he was a member of Psi Upsilon and Scroll and Key.
He attended Harvard Law School for a year and then continued studying law in Washington, D.C. while he worked as private secretary for William B. Allison, a United States Senator from Iowa. He was admitted to the bar in 1893 and commenced practice in New York City.
Active in politics as a Republican, Sheffield was elected to the New York State Assembly in 1893 and served one term. From 1895 to 1898, he was a member of New York City's Board of Fire Commissioners, and he was the board's president in 1897 and 1898. He was a delegate to every New York State Republican Convention from 1896 to 1924>and a delegate to the Republican National Conventions of 1916, 1920, 1924, and 1936. He was active in judicial reform movements and other efforts to improve local government in New York City.
He was twice offered appointment to the federal bench during the Theodore Roosevelt presidency, both of which he declined. He was also a friend and political ally of Charles Evans Hughes, who was United States Secretary of State from 1921 to 1925. He served as President of The Union League Club from 1921-1924.