Often eaten on St. Patrick's Day, corned beef and cabbage is Irish-American in origin. The dish evolved from traditional Irish meals of smoked pork and potatoes as Irish-Americans substituted other ingredients more readily available in the United States.
Before immigrating to the United States, the Irish mostly ate pork for meat. In Ireland, beef was very expensive, and the Irish used cows for their strength and milk rather than as a regular meat source. The Irish favored smoked pork loin, similar to modern Canadian bacon. However, in the United States, pork was prohibitively expensive. Additionally, Irish immigrants often lived in poor areas with other immigrants that also faced persecution, including Jewish immigrants. Irish-Americans gradually started to buy meat from Jewish butchers, including corned beef on special occasions.
As Irish-Americans transformed St. Patrick's Day from a religious feast day into a celebration of their heritage, they used the occasion to spend their money on corned beef from local Jewish stores. Irish-Americans combined corned beef with traditional potatoes and the cheapest vegetable available, which was cabbage.
The popularity of corned beef and cabbage never reached Ireland itself, where most people still eat pork or lamb on St. Patrick's Day. In fact, many American St. Patrick's Day traditions did not reach Ireland until the late 20th century. Irish laws even prohibited Irish pubs from opening on St. Patrick's Day until 1970.