Research by Prof. Haemig of Luther Seminary, St. Paul, points to Johann Hinrich Wichern (1808–1881), a Protestant pastor in Germany and a pioneer in urban mission work among the poor, as the inventor of the modern Advent wreath in the 19th century. During Advent, children at the mission school "Rauhes Haus", founded by Wichern in Hamburg, would ask daily if Christmas had arrived. In 1839, he built a large wooden ring (made out of an old cartwheel) with 20 small red and 4 large white candles. A small candle was lit successively every weekday and Saturday during Advent. On Sundays, a large white candle was lit. The custom gained ground among Protestant churches in Germany and evolved into the smaller wreath with four or five candles known today. Roman Catholics in Germany began to adopt the custom in the 1920s, and in the 1930s it spread to North America. Professor Haemig's research also indicates that the custom did not reach the United States until the 1930s, even among German Lutheran immigrants.