| Thomas B. Shannon | |
| Office: | 19th Speaker of the California State Assembly |
| Term: | December 1871–April 1872 |
| Predecessor: | George H. Rogers |
| Successor: | Morris M. Estee |
| Office1: | Member of the California State Assembly from the 8th district |
| Term1: | 1871-1872 |
| State2: | California |
| District2: | at-large |
| Predecessor2: | Aaron A. Sargent |
| Successor2: | John Bidwell |
| Term Start2: | 4 March 1864 |
| Term End2: | 3 March 1865 |
| Office3: | Member of the California State Assembly from the 14th and 24th districts |
| Term3: | 1859-1862 |
| Birth Name: | Thomas Bowles Shannon |
| Birth Date: | 21 September 1827 |
| Birth Place: | Westmoreland County, Pennsylvania, U.S. |
| Death Place: | San Francisco, California, U.S. |
| Party: | Republican Democratic (formerly), Whig (formerly) |
Thomas Bowles Shannon (September 21, 1827 – February 21, 1897) was a California merchant and politician who served as member of the California State Assembly and the U.S. House of Representatives for California.
Shannon was born on September 21, 1827, in Westmoreland County, Pennsylvania.[1] He attended the Westmoreland County public schools. He moved to Illinois in 1844 and by 1849 he moved during the California Gold Rush, to California. There he engaged in mining and mercantile pursuits in Plumas County in California.
Shannon was originally a Whig in politics, but later supported the Free Soil wing of the Democratic Party, serving as a member of the California Central Committee in 1860. He subsequently switched to the Republican Party. He was a member of the California State assembly in 1859, 1860, and 1862, representing Plumas County. He supported black testimony in the California courts in 1862 and 1863, a position the Democrats unsuccessfully used against him as an issue in his third campaign for the Assembly and his subsequent campaign for Congress.
Running as a supporter of Senator John Conness, Shannon was elected as a Republican to the Thirty-eighth Congress (March 4, 1863 – March 3, 1865), in which he served as chairman of the Committee on Expenditures in the Department of the Interior. As a congressman he participated little in debate, but voted consistently for administration measures. Due to political turmoil in California over Conness, Shannon was not a candidate for reelection in 1864. He was selected as a California Congressional delegate for the Lincoln funeral, in which capacity he participated in speeches delivered outside the capital building in Columbus, Ohio.
Shannon was appointed surveyor at the port of San Francisco on August 11, 1865, and served until March 16, 1870.[2] He was again a member of the State Assembly, representing San Francisco, in 1871 and 1872, serving as the Speaker of the Assembly the first year.[3]
He was appointed by President Grant appointed him Collector of Customs at San Francisco, which he served as from July 1, 1872, to August 10, 1880, after which he resumed his mercantile pursuits.
Shannon died in San Francisco, California, on February 21, 1897. His body was originally buried in the Masonic Cemetery, but reburied in 1931 at Woodlawn Memorial Park Cemetery in Colma, California.