The meal that became a St. Patrick’s Day staple across the country—corned beef and cabbage—was an American innovation. While ham and cabbage were eaten in Ireland, corned beef offered a cheaper substitute for impoverished immigrants. Irish-Americans living in the slums of lower Manhattan in the late 19th century and early 20th, purchased leftover corned beef from ships returning from the tea trade in China. The Irish would boil the beef three times—the last time with cabbage—to remove some of the brine.
Or so the story goes, but I have my own story.
From the arrival of poor Irish immigrants in the 1840's up through WW1, I posit that immigrants ate a lot of horse meat. Either knowingly or unknowingly, and that when corned "beef" and cabbage became popular in the early 1900's, it was likely made with horse meat.
In the 1890's horse drawn street cars were replaced with electric ones and for the next 20 years nearly all horse drawn carriages would be replaced by cars. As a result millions of horses were slaughtered and found their way into the food stream. Horse meat, described as lean, stringy, gamey or tasteless, probably fit the bill well for corning. Oh, and it was cheap.
The latest incidence of horse meat ending up in corned beef that I could find was in 2013 in England.
Since 2017 the Trump administration has tried twice to lift the ban on horse meat in the U.S.
So who knows, you might be eating "real" corned "beef" in the near future.