The Battle of Point Pleasant or the Battle of San Jacinto could be considered among the shortest battles in US history, while the Battle of Gettysburg had the most overall casualties, and the Battle of Antietam the most in a single day.
Step-by-step explanation:
The question "What was the shortest battle in US history?" refers to a historical event. However, the context provided seems to refer to a different battle which began unexpectedly on July 1 when both armies inadvertently encountered each other while moving to their positions. This is reminiscent of the Battle of Gettysburg during the Civil War, although this was not the shortest battle in American history. The shortest recorded battle in US history is likely the Battle of Point Pleasant during the American Revolution, which lasted for less than a day, or possibly the Battle of San Jacinto in the Texas Revolution which lasted a mere 18 minutes.
Regarding the 'Test Yourself' section, the battle with the most overall casualties in the Civil War is commonly understood to be the Battle of Gettysburg. The battle with the most casualties in a single day is typically cited as the Battle of Antietam.