American Soldiers of the 6th US Cavalry Regiment Training Horses in Fort Bayard, New Mexico (1880's)

American soldiers of the 6th US Cavalry Regiment training horses in Fort Bayard, New Mexico, c. 1885.

Source: National Archives and Records Administration.

Animated Stereoview of an African American Man at the Reins of a Horse-Drawn Cart Carrying Cotton in Gainesville, Florida (1800's)

Animated stereoview of an African American man at the reins of a horse-drawn cart carrying cotton in Gainesville, Florida, c. 1800's.

Source: New York Public Library.

Portrait of a Boat Girl in Canton (Guangzhou), China, by Scottish Photographer John Thomson (1869)

Portrait of a boat girl in Canton (Guangzhou), China, by Scottish photographer John Thomson, 1869.

Source: Wellcome Images.

Animated Stereoscopic Portrait of Republican Member of the U.S. House of Representatives From Pennsylvania Stephen Fowler Wilson Taken by Mathew Brady (1860's)

Animated stereoscopic portrait of Republican member of the U.S. House of Representatives from Pennsylvania Stephen Fowler Wilson taken by Mathew Brady, c. 1860's.

Source: National Archives and Records Administration.

Tintype Portrait of Confederate Cavalrymen Posing in a Camp in Georgia During the American Civil War (1860′s)

Tintype portrait of Confederate cavalrymen and unidentified African American man, possibly a camp servant, posing in a camp in Georgia during the American Civil War, c. 1860′s.

Source: Missouri History Museum.

Portrait of an Unidentified Mounted Union Officer Posing With an African American Camp Servant in a Camp During the American Civil War (1860′s)

Portrait of an unidentified mounted Union officer posing with an African American camp servant in a camp during the American Civil War, c. 1860′s.

Source: Library of Congress.

Carte De Visite Portrait of German Field Marshal Helmuth Von Moltke the Elder (1870′s)

Carte de visite portrait of German field marshal Helmuth von Moltke the Elder, c. 1870′s.

Source: Rijksmuseum.

Two Views of Exhibits in the Interior of Linnaean Hall at the Gettysburg College in Gettysburg, Pennsylvania (1870′s/1880′s)

Two views of exhibits in the interior of Linnaean Hall at the Gettysburg College in Gettysburg, Pennsylvania, c. 1870′s/1880′s. By William H. Tipton. From The Pennsylvania College Book 1832-1882 published in 1882.

Portrait of Union Artillerymen of the 1st Illinois Light Artillery Regiment Posing in Their Dining Hall in Camp Smith in Cairo, Illinois (1861)

Portrait of Union artillerymen of the 1st Illinois Light Artillery Regiment posing in their dining hall in Camp Smith in Cairo, Illinois, 1861. The roof of the structure was made from the shell of a decayed sycamore tree. The men are identified from left to right as: George L. Whittier, Wallace Ames, Chauncey R. Crandall, W. L. Southworth. From the book History of Battery "A" First Illinois Light Artillery Volunteers by Charles B. Kimbell originally published in 1899.

Portrait of Ojibwe Chief Hole in the Day (1860′s)

Portrait of Ojibwe chief Hole in the Day, c. 1860′s. By Mathew Brady.

Source: National Archives and Records Administration.