Question: What type of criminals, named after a term from the Revolutionary War, were involved in the Clay County Savings Association Building robbery?

Context paragraphs:
Clay County Savings Association Building: The Clay County Savings Association in Liberty, Missouri, was robbed on February 13, 1866, making it one of the earliest documented daylight bank robberies.  The robbers escaped with at least $60,000 ( ) and killed a bystander outside.  The robbery is believed to have been conducted by a group of former Confederate guerrillas, possibly led by Jesse James or Archie Clement, which became known as the James–Younger Gang.

Edina Double Square Historic District: Edina Double Square Historic District is a national historic district located at Edina, Knox County, Missouri.  The district encompasses 37 contributing buildings in the central business district of Edina.  It developed between about 1865 and 1945 and includes representative examples of Italianate and Streamline Moderne style architecture.  Notable contributing buildings include the Public Works Administration funded Knox County Courthouse (1934-1935) designed by William B. Ittner, Bishoff Bakery (1891), Northern Hotel (1860s), Ennis House/Northern Hotel (c. 1865), Edina School and Gymnasium (1915-1916), D. H. Mudd Building (c. 1904), Phillip Linville Building (c. 1908, c. 1963), Tobias J. Lycan Building (c. 1891), Jacob Pugh Building (c. 1891), Albert G. Bostick Building (c. 1891), Knox County Savings Bank (c. 1891), Thomas Burk Buildings (c. 1881), Bank of Edina Building (c. 1907), Joseph F. Biggerstaff Buildings (c. 1881), Stablein Building (c. 1870), and Knox County Public Library (c. 1915).

Bushwhacker: Bushwhacking was a form of guerrilla warfare common during the American Revolutionary War, American Civil War and other conflicts in which there were large areas of contested land and few governmental resources to control these tracts.  This was particularly prevalent in rural areas during the Civil War where there were sharp divisions between those favoring the Union and Confederacy in the conflict.  The perpetrators of the attacks were called bushwhackers.  The term "bushwhacking" is still in use today to describe ambushes done with the aim of attrition.

Clay County Courthouse (Alabama): The Clay County Courthouse is a historic courthouse building in Ashland, Clay County, Alabama.  The Classical Revival-style building has served as the county courthouse since its completion in 1906.  Notable characteristics include its large dome, with clocks inset on four sides, and cupola surmounted by a statuary representing justice.  It was added to the National Register of Historic Places on November 21, 1976.

Claycomo, Missouri: Claycomo is a village in Clay County, Missouri, United States.  The village’s name is a portmanteau of "Clay, Co" (Clay County), and "Mo" (Missouri).  The population was 1,430 at the 2010 census.  Ford Motor Company has an assembly plant in Claycomo.  Kansas City Assembly is responsible for building the Ford F-150 pickup trucks and the Ford Transit vans.

Savings Bank Building: The Savings Bank Building is a commercial building located at 101 South Front Street in Marquette, Michigan.  It is also known as the Marquette County Savings Bank.  The building was designated a Michigan State Historic Site in 1976 and listed on the National Register of Historic Places in 1978.

Old Clay County Courthouse (Clay, West Virginia): The Old Clay County Courthouse in Clay, West Virginia was designed by Frank L. Packard and built in 1902.  The Beaux-Arts building was located on a hill overlooking the county seat.  The courthouse was the site of three notable trials: the Sarah Ann Legg trial of 1905, the first trial of a woman in Clay County for murder, the Booger Hole trial of 1917, in which citizens nearly lynched the defendants, and the Oscar Bail trial of 1953, in which Bail was convicted of killing a mine guard in the Great Widen Coal Strike.

Onondaga County Savings Bank: The Onondaga County Savings Bank was chartered in 1855 in Syracuse, New York.  It was a franchise ahead of its time and had four separate branches by the late 19th century.  The "Onondaga County Savings Bank Building" was constructed in 1896 adjacent to the Erie Canal in "Clinton Square".

Clay County, Tennessee: Clay County is a county located in the U.S. state of Tennessee.  As of the 2010 census, the population was 7,861.  Its county seat and only incorporated city is Celina.  Clay County is named in honor of American statesman Henry Clay, member of the United States Senate from Kentucky and United States Secretary of State in the 19th century.  Its current mayor is Dale Reagan.

Clay County Courthouse (Illinois): The Clay County Courthouse, located at 300 Broadway Street in Louisville, is the county courthouse serving Clay County, Illinois.  Built in 1913, the courthouse was Clay County's fourth courthouse; it has served continuously as the seat of Clay County government since its opening.  Architect Joseph W. Royer, who planned several other Illinois courthouses, designed the Classical Revival building.  The courthouse was added to the National Register of Historic Places in 2015.

Supporting paragraphs: Clay County Savings Association Building Bushwhacker
Answer: bushwhackers