Deadlines were common forms of crowd control in military prisons of the Civil War era, especially open stockade type prisons. What constituted the deadline varied widely from prison to prison. At many prisons, such as Andersonville, Camp Lawton, Camp Douglas, and Florence, the deadline was a low rail fence. At the stockade on Morris Island near Charleston, the deadline was a series of stakes with rope tied between them. At Belle Isle it was an embankment and trench. At several of the coastal fortifications, a deadline was not necessary, as prisoners were confined in the casemates. Interestingly, Elmira did not have a deadline, even though it was a stockade prison. The deadline at Rock Island consisted of a series of white stakes that were illuminated by lanterns at night.  Any prisoner crossing that line took the chance of being shot.

The Camp Sumter military prison at Andersonville was one of the largest Confederate military prisons during the Civil War. It was designed for a maximum of 10,000 prisoners. At its most crowded, it held more than 32,000 men, many of them wounded and starving in horrific conditions with rampant disease, contaminated water, and only minimal shelter from the blazing sun and the chilling winter rain.  During the 14 months the prison existed, more than 45,000 Union soldiers were confined here. Of these, almost 13,000 died here. 2011 to 2015 marks the 150th anniversary of the American Civil War. 

Like many military phrases, American business has adapted the term to mean the time limit to complete a job – often at the risk of being "shot" if that limit is crossed.

Top image shows prisoners at Andersonville (Georgia) Prison.  Andersonville National Historic Site is the only park in the National Park System to serve as a memorial to all American prisoners of war.