When John Geyser is shown making his drawings, the sketches you can see in the wide and medium shots rarely match the close-ups of the drawings. Most notably in the John Brown trial sequence, the wide shots show John has just a few doodles or sketchy outlines on his drawing pad, then we cut to a close-up of highly detailed, finished artwork.
The series shows Lincoln giving the Gettysburg address which occurred in November 1863 then shows the fall of Vicksburg which occurred in July 1863.
When John Brown is hanged for the uprising at Harper's Ferry, the apple trees are in full blossom. John Brown was hanged on 2 December 1859.
The scene showing the First Battle of Bull Run shows the trees without leaves, indicating autumn or winter time. The battle actually took place in July, so the trees would be full of leaves.
In the Civil War the primary infantry weapon was the muzzle-loading musket. For close up shots most of the soldiers use the British made .577 Pattern 1853 Enfield Rifle Musket, which was imported in large quantities during the Civil War by both sides. However, in many scenes (especially the Vicksburg scene with victorious Union troops) many of the soldiers can be seen carrying the .45-70 U.S. Model 1873 Trapdoor Springfield rifle, a shortened breech-loading version of the U.S. Model 1861 Springfield Rifle Musket.
During the scene where Lincoln and Captain Steele test the new repeating rifle, you can see cars driving in the background. Lincoln also walks away on an obviously modern concrete sidewalk.
Along the road that leads to the Geyser farm. You can see wire fence that is set up along the field. Wire fence was not invented until the 1870s.
As Lincoln and Captain Steele are walking after testing the new repeating rifle, Modern street lamp posts can be seen.
On the DVD release version, during the first Bull Run battle scene (set in 1861), a helicopter used to film scenes from the air is visible flying from left to right across the screen above the house on the hill.