A good sidearm is the ultimate plan B. You don't want to have to use it, but if you do have to — it better work. They're kind of the last line of defense for American freedom and they've come a long way in 240-plus years.
The sidearm has gone from a smoothbore, muzzle-loaded, single shot to SIG Sauer's new, modular, 59-round monster which is also customizable for every user. No matter what your opinion of them might be, if they've ever kept you in the fight for even a minute longer, then they did their job.
These are most important sidearms the US military has adopted over the last couple hundred years.
1. Harper's Ferry Model 1805
This was the first pistol ever made by a US national armory. It was a flintlock pistol that lasted well into the Mexican War — but not for any particular reason besides apathy. They were heavy and tended to misfire. The Military Police Corps insignia still bears crossed 1805s to this day.
2. Colt M1847 Walker
The Colt Walker Older Firearms/Flickr/Wikimedia Commons
Welcome to the dawn of a new era. This was the first mass-produced revolver and, at an astonishing 15 inches long, it was able to make its way down south in time to win the Mexican War. The "Walker" in its name comes from the Texas Ranger who helped design the .44-caliber weapon. (No, it was not Chuck Norris.)
3. Colt M1848 Dragoon
The Colt Dragoon Mod 1848. Hmaag/Wikimedia Commons
The 1847 held a lot of black powder, so when they exploded (as they sometimes did), it turned people off to the idea of buying another Colt firearm, which was bad for business. The 1848 revolver didn't require so much powder — for a .44-caliber pistol, anyway. This weapon lived on all the way through the Civil War.
4. Colt M1860 Army
An early model Colt Army 1860. Hmaag/Wikimedia Commons
This is a more powerful, updated version of a similar model Colt made for the US Navy. It was widespread in the American Civil War by anyone who carried a sidearm (and by many who weren't supposed to).
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5. Remington New Model
A Remington Model 1858 on display at Morges military museum. Rama/Wikimedia Commons
Colt's weapons production factory burned down in 1864 and the Army was still in the middle of fighting the Civil War, so they had to turn somewhere. Meanwhile, Remington's sidearms had became more accurate without sacrificing the stopping power needed to tame the American frontier.
6. Colt M1873 Single Action Army
Remington had a good run, but when it comes time to win the west, you need an American classic. And what could be more classic than a name that's still known over 100 years later? We're talking, of course, about the Colt .45. It was the standard-issue sidearm until 1892 and "The Peacemaker" also became synonymous with cowboys. This sidearm was commonly seen well into the 20th Century.
7. Colt M1892 Double Action Army-Navy
The Colt Model 1892. Hmaag/Wikimedia Commons
This was Colt's first double-action sidearm with a swing-out cylinder made for the US military. The caliber was reduced to a .38, which was fine in most cases, but it famously was unable to stop charging Filipino freedom fighters, even with multiple shots, even at close range.
8. Colt M1911
The legend. This weapon is more than 100 years old and is still used by Army and Navy special operators. They sure don't make 'em like they used to. Easily one of the most common firearms in the world to this day, this bad boy fought in almost every conflict from World War I to today.
9. Beretta M9
The Beretta had a troubled history. From the ammunition pressure to slide failure injuries to a lack of confidence in the weapon's performance and stopping power, the M9 was generally not accepted as one of the premiere firearms in American history. It had the lowest approval rating of any weapon used by troops in Iraq or Afghanistan.
The M1911 is a tough act to follow.