Question: Walker County was named after which member of the US Senate from Mississippi?

full_context: Document 1: Norman R. Walker: Norman Ray "Doc" Walker (July 28, 1889 – April 5, 1949) was a Canadian-born American pharmacist and politician, best known as the longest-serving member of Alaska's territorial legislature. Born in Regina, Saskatchewan, Walker emigrated to the United States as a youth, later serving in the United States Army and attending Washington State University. He was a pharmacist in Seattle, Washington and then moved to Ketchikan, Alaska and owned the Walker-Broderick House. Walker served as mayor of Ketchikan from 1930 to 1932 and then served in the Alaska Territorial Senate from 1933 until 1947. He lost reelection to his Senate seat in 1948 after feuding with territorial governor Ernest Gruening over Gruening's efforts to overhaul the territory's tax structure. Walker was also head of the Alaska Territorial Pharmacy Board.
Document 2: Walker County Jane Doe: Walker County Jane Doe is an unidentified murder victim discovered on November 1, 1980, in Huntsville, Walker County, Texas. After the investigation of her murder and identity went cold, she was buried in a donated casket in Oakwood Cemetery in the same town where she was found. To this day, she has yet to be identified, even though her face has been reconstructed several times.
Document 3: Union County, Mississippi: Union County is a county located in the U.S. state of Mississippi. As of the 2010 census, the population was 27,134. Its county seat is New Albany. According to most sources, the county received its name by being a union of pieces of several large counties, like other Union counties in other states. However, other sources say that the name was meant to mark the re-union of Mississippi and the other Confederate states after the Civil War (at the time, the state had a Republican government under Reconstruction) or that the name came from the Union District, South Carolina, where many of the area's first European-American settlers came from. It is possible that there was more than one reason for the name.
Document 4: Fort Davis, Texas: Fort Davis is a census-designated place (CDP) in Jeff Davis County, Texas, United States. The population was 1,201 at the 2010 US Census . It is the county seat of Jeff Davis County. It was the site of Fort Davis established in 1854 on the San Antonio-El Paso Road through west Texas and named after Jefferson Davis, who was then the Secretary of War under President Franklin Pierce.
Document 5: Robert Ward Johnson: Robert Ward Johnson (July 22, 1814 – July 26, 1879) was an American politician who served as a Confederate States Senator from Arkansas (1862-1865). He previously served as a U.S. Representative (1847-1853), Senator (1853-1861), and delegate to the Provisional Congress of the Confederate States (1861-1862).
Document 6: Bob Dole: Robert Joseph Dole (born July 22, 1923) is an American lawyer and politician who represented Kansas in Congress from 1961 to 1996 and served as the Republican Leader of the United States Senate from 1985 until 1996. He was the Republican presidential nominee in the 1996 presidential election and the party's vice presidential nominee in the 1976 presidential election.
Document 7: Louis McLane: Louis McLane (May 28, 1786 – October 7, 1857) was an American lawyer and politician from Wilmington, in New Castle County, Delaware, and Baltimore, Maryland. He was a veteran of the War of 1812 and a member of the Federalist Party and later the Democratic Party. He served as the U.S. Representative from Delaware, U.S. Senator from Delaware, U.S. Secretary of the Treasury, U.S. Secretary of State, Minister Plenipotentiary to the United Kingdom, and President of the Baltimore and Ohio Railroad. As a member of President Andrew Jackson's Cabinet, McLane was a prominent figure during the Bank War. McLane pursued a more moderate approach towards the Second Bank of the United States than the President, but agreed with Jackson's decision in 1832 to veto a Congressional bill renewing the Bank's charter. He also helped draft the Force Bill in 1833.
Document 8: Robert J. Walker: Robert John Walker (July 19, 1801November 11, 1869) was an American lawyer, economist and politician. An active member of the Democratic Party, he served as a member of the U.S. Senate from Mississippi from 1835 until 1845, as Secretary of the Treasury from 1845 to 1849 during the administration of President James K. Polk, and briefly as Territorial Governor of Kansas in 1857.
Document 9: John Walker (Arkansas politician): John Winfield Walker is an American politician and a Democratic member of the Arkansas House of Representatives representing District 34 since January 2011. John W. Walker was born in Hope, Arkansas where he attended Yerger High School until 1952. In 1965, Walker began the general practice of law in Little Rock, Arkansas with the emphasis on civil rights. In 1968, he opened one of the first three racially integrated law firms in the south, first known as Walker and Chachkin. Between 1965 and now, Walker has personally been involved in most of the reported cases which involve racial discrimination in the state of Arkansas. Many of them are landmark having created new law and opened doors to school houses and work places throughout the state of Arkansas and surrounding states. One case has continued to take his time since 1965, the Little Rock school case started by the late Wiley Branton and LDF general counsel/later Supreme Court Justice Thurgood Marshall. Many of Walker’s early cases involved classes of people discriminated against due to their race in mega corporate environments. A recent case of Walker’s was the only nationwide racial discrimination case ever successfully prosecuted against Wal-Mart. It involved a class of African American truck drivers.
Document 10: Dodge, Texas: Dodge is an unincorporated community in eastern Walker County, Texas, United States, on the northern edge of the Sam Houston National Forest. It lies along FM 405 east of the city of Huntsville, the county seat of Walker County. Its elevation is 400 feet (122 m). Although Dodge is unincorporated, it has a post office, with the ZIP code of 77334; the ZCTA for ZIP Code 77334 had a population of 184 at the 2000 census.
Document 11: Jeff Davis County Courthouse (Texas): The Jeff Davis County Courthouse is located in the town of Fort Davis, the seat of Jeff Davis County in the U.S. state of Texas. The courthouse was constructed between 1910-1911 and added to the National Register of Historic Places in 2002. The Texas Historical Commission (THC) has also designated the building as a Recorded Texas Historic Landmark since 2000 and, along with the surrounding courthouse square, as a State Antiquities Landmark since 2003. The surrounding county and county seat, along with the nearby historic frontier fort at Fort Davis National Historic Site, are named after Jefferson Davis, who served as U.S. war secretary at the time of the establishment of the fort and the town, and who would later become president of the Confederate States of America during the Civil War.
Document 12: Jeff Davis County, Texas: Jeff Davis County is a county in the U.S. state of Texas. As of the 2010 census, its population was 2,342. Its county seat is Fort Davis. The county is named for Jefferson Davis, who served as the 23rd United States Secretary of War in the 1850s, and then, during the American Civil War, as President of the Confederate States of America. Jeff Davis County is easily recognizable for its unique shape; it is a pentagon which has no north-south nor east-west boundaries, save for a six mile line serving as its southern boundary. it also is the "only" county in the United States that touches a foreign country (Mexico) at a single point. Jeff Davis is also one of the nine counties that compose the Trans-Pecos region of West Texas.
Document 13: James K. Polk: James Knox Polk (November 2, 1795 – June 15, 1849) was the 11th President of the United States (1845–49). He previously served as the 13th Speaker of the House of Representatives and as Governor of Tennessee. A protege of Andrew Jackson, Polk was a member of the Democratic Party and an adherent of Jacksonian democracy and Manifest Destiny. During his presidency, the United States expanded significantly with the annexation of Republic of Texas, the Oregon Treaty, and the conclusion of the Mexican-American War.
Document 14: Walker County, Texas: Walker County is a county located in the east central section of the U.S. state of Texas. As of the 2010 census, its population was 67,861. Its county seat is Huntsville. Initially, Walker County was named for Robert J. Walker, a legislator from Mississippi who introduced into the United States Congress the resolution to annex Texas. Walker later supported the Union during the Civil War and earned some enmity. In order to keep the county's name, the state renamed it for Samuel H. Walker, a Texas Ranger and soldier in the American Army.
Document 15: Gilmer, Texas: Gilmer is a town in and the county seat of Upshur County, Texas, United States. It is best known for being the home of the East Texas Yamboree, as well as the birthplace of popular music singers Don Henley of the Eagles band and Johnny Mathis, as well as blues musician Freddie King. The population was 4,905 at the 2010 census. The city's namesake is a former United States Secretary of the Navy, Thomas Walker Gilmer.
ground_truth: Robert J. Walker