Stereoview of Cuban Rebels in a Trench During the Spanish-American War Titled “Cubans in Their Trenches - Awaiting the Spaniards - Pinar del Río, Cuba.” (1898)

“Cubans in their trenches - Awaiting the Spaniards - Pinar del Río, Cuba.” Cuban rebels during the Spanish-American War, c. 1898. Published by Strohmeyer and Wyman.

Source: Library of Congress.

An American Soldier Firing a Chauchat Light Machine Gun From Behind a Barricade Made of Sandbags and Ammunition Boxes During World War 1 (1910's)

An American soldier firing a Chauchat light machine gun from behind a barricade made of sandbags and ammunition boxes during World War 1.

American Troops Aiming Their Rifles Down a Road in Bonvillers, France (1918)

American troops aiming their rifles down a road in Bonvillers, France, May 22, 1918. Possibly an authentic combat photograph.

Source.

Daguerreotype Portrait of a Group of Men Posing in Front of a Building Somewhere in the United States (1850)

Daguerreotype portrait of a group of men posing in front of a building somewhere in the United States, c. 1850.

Source.

Entrenched Boer Artillery and Soldiers Posing For a Photograph During the Siege of Ladysmith in Natal, South Africa, During the Second Boer War (1899)

Entrenched Boer artillery and soldiers posing for a photograph during the Siege of Ladysmith in Natal, South Africa, during the Second Boer War, c. 1899.

Source.

British Soldiers Posing Having a Mock Skirmish (1861)

British soldiers posing having a mock skirmish, 1861. By Edward Dyne Fenton.

Source.

Policemen Aiming Their Revolvers During a Longshoremen's Strike in San Francisco

Policemen aiming their revolvers during a longshoremen's strike in San Francisco, c. 1930’s.

Source.

Union Zouaves of the 4th Michigan Volunteer Infantry Regiment Posing as if Fighting in Combat During the Civil War

"Picket Guard on the alert." A group of Union Zouaves from the 4th Michigan Volunteer Infantry Regiment posing as if fighting in combat during the Civil War. Animated stereoview.

Source.
More information.

A sharper version of one half of the stereoview. Source.

Two Union African American Soldiers Aiming Their Muskets from Behind Cover Near the Dutch Gap Canal

Two Union African American soldiers aiming their muskets from behind cover near the Dutch Gap Canal, Virginia, 1864. Animated stereoscopic photographs.

Source.