Usually made with dried peas, pea soup (or split pea soup) is a popular dish in the diets of many cultures. Depending on the variety of pea used to cook it, pea soup usually has a beige/yellow or green/grey colour. The soup has been around for millennia.
Ireland and Britain
In the 18th century, "pease pudding" was a low-cost and high-protein staple food. The pudding (or soup in a slightly runnier form) was made of dried peas that were easy to store in large quantities. This made pea soup the perfect food for sailors, especially when it was boiled along with salt pork; this marks the beginning of the modern ham and pea soup. While peas were largely replaced by potatoes as a staple food by the time 19th century rolled around, a variation of classic pea soup is still popular in the diet of both countries - "mushy peas". This is a common side dish for meat pies, and especially fish and chips.
Pea soup (or soupe aux pois, rather) is a traditional Quebec dish. Sources say the most authentic version of Quebec pea soup is most likely made of whole yellow peas, herbs and salted pork. The pork is often taken out once cooked, chopped up, and put back in the soup. Another option is to remove the ham once cooked and serve thin slices of it separately.
Pea soup in Newfoundland usually has more vegetables, like carrots and turnips and carrots. It's commonly served with dumplings.
In Germany, pea soup often has meat such as sausage, bacon or Kassler (that is, cured and smoked pork). Ingredients depend largely on which region you're in. One popular way to serve pea soup in Germany is with several sausages (or Wurste) and dark bread. Either traditional or instant pea soup is used to make the dish.
One of the first instant products ever created was pea soup. It consisted mainly of beef and pea meal and it was called fat "Erbswurst" (or pea sausage). Johann H. Gruneberg invented it in 1867. He would eventually sell the pea soup recipe to the Prussian state. Upon the advent of the Franco-Prussian War, the War Ministry constructed a big manufacturing plant and produced nearly 5,000 tons of pea sausage to feed its soldiers. Knorr purchased the Erbswurst license in 1889 and continues to produce it to this day.
Pea soup has also been a staple in the national diet of the Netherlands, Holland, Sweden, Finland, Scandinavia and the United States for centuries.