You can also soak or rinse and boil your canned corned beef in water to draw out the sodium before cooking. If water isn't doable, simply add some sugar to balance out the salt.
Canned foods are vacuum-packed and typically have preservatives. While shelf life can vary, brands typically don't extend canned goods that far into the future.
However, canned corned beef predates the Civil War by several decades and didn't originate in the US. By 1819, the process for preserving roast beef was patented.
Corned beef is a St. Patrick's Day staple, partially due to its historic popularity with the Irish American community. It's a fan favorite among the Irish.
However, it has its place in other international cuisines. European colonies in the Caribbean and Southeast Asia helped make canned corned beef a central part of many diets.