Served in the Mexican-American War

http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GRid=13252440

S Congressman. Elected to represent Tennessee's 6th District n the United States House of Representatives, he served from 1851 to 1853. He also served as a Member of the Tennessee State House of Representatives from 1842 to 1845, and as United States Minister to the Two Sicilies from 1845 to 1847. A major in the United States Army during the Mexican War, he was the brother of United States President James Knox Polk.

http://en.wikipedia.org/wiki/William_Hawkins_Polk

William H. Polk was born in Maury County, Tennessee, on May 24, 1815. He attended the city schools of Columbia, and the University of North Carolina in 1832 and 1833. He graduated from the University of Tennessee at Knoxville, studied law, was admitted to the bar in 1839, and commenced practice in Columbia. He was a member of the Tennessee House of Representatives from 1842 to 1845. He served as America's Minister to the Kingdom of the Two Sicilies (in present-day Italy) from March 13, 1845 to August 31, 1847. He served as major of the Third Dragoons in the Mexican-American War in 1847 and 1848.

He was elected as an Independent Democrat to the Thirty-second Congress, serving from March 4, 1851 to March 3, 1853. He afterward resumed the practice of law, and died in Nashville on December 16, 1862. He was interred in Greenwood Cemetery in Columbia.

http://familytreemaker.genealogy.com/users/p/o/l/Billy-F-Polk/GENE13-0057.html

. WILLIAM HAWKINS4 POLK, SON SAMUEL POLK/JANE KNOX (SAMUEL3, EZEKIEL2, WILLIAM1) was born 24 May 1815 in Maury Co., TN., and died 16 Dec 1862 in Nashville, Davidson Co., TN.16407,16408,16409.

He married (1) BELINDA G. DICKINSON 18 Apr 1837 in Maury Co., TN., probablyShe was born Aft. 1814, and died 26 Mar 1844 in Nashville, Davidson Co., TN., at the home of her father. 

He married (2) MARY LOUISA CORSE 29 Jun 1847 in New York City, NY.. She was born Abt. 1824 in NY.16425, and died 02 Apr 1851

He married (3) LUCY EUGENIA WILLIAMS 14 Jul 1854 in Montmorenci, (Warren Co. ?) NC.. She was born 10 Oct 1826 in White Rock, Halifax Co., NC., OR Warren Co., NC., (See notes), and died 11 Jan 1906 in Warren Co., NC.,