One such enterprising individual was Sam Rosen. A Polish-born immigrant Rosen had first moved to Germany to learn the art of baking. He first came to New York and opened a bakery at the unbelievable age of 16. Seeking better fortune only a few years later he came west to Chicago, buying a bakery and opening his eponymous business in 1909. It was a huge success, not only on the strength of its rye bread beloved by the Germans and Poles of Chicago, but as the originator of the poppy-seed bun. It was another essential ingredient in the Chicago dog, introduced by an upstart, enterprising immigrant, tailored to the tastes of a diverse city.
By the 1920s Maxwell St on the West Side was the center of Chicago's immigrant community. A bustling market where Jewish, Italian, Greek, and Polish traders would sell clothes, trinkets, and food. Hot dogs were the dominant meal for the busy cost-conscious crowds that would fill the streets hawking their wares. Many of these vendors also owned vegetable stands, and they began to experiment with a wide range of toppings plucked fresh from the market. Up until the '20s traditional German/Jewish toppings like mustard and pickles had been how someone would take their dog. Now, according to Hot Dog historian Bruce Kraig, vendors began adding their own spicy and sour flavor profiles -- from hot peppers, cabbage, and celery salt -- that appealed to the tastes of the new ethnic groups.