that was opened in 1847 by Cyrus Hall McCormick. It was a processing center for natural resource commodities extracted in the West. The Wisconsin forests supported the millwork and lumber business; the Illinois hinterland provided the wheat. Hundreds of thousands of hogs and cattle were shipped to Chicago for slaughter, preserved in salt, and transported to eastern markets. By 1870, refrigerated cars allowed the shipping of fresh meat to cities in the East. The prairie bog nature of the area provided a fertile ground for disease-carrying insects. In springtime, Chicago was so muddy from the high water that horses could scarcely move. Comical signs proclaiming "Fastest route to China" or "No Bottom Here" were placed to warn people of the mud. Travelers reported Chicago was the filthiest city in America. The city created a massive sewer system. In the first phase, sewage pipes were laid across the city above ground and used gravity to move the waste. The city was built in a low-lying area subject to flooding. In 1856, the city council decided that the entire city should be elevated four to five feet by using a newly available jacking-up process. In one instance, the five-story Brigg's Hotel, weighing 22,000 tons, was lifted while it continued to operate. Observing that such a thing could never have happened in Europe, the British historian Paul Johnson cites the astounding feat as a dramatic example of American determination and ingenuity based on the conviction that anything material is possible. Immigration and population in 19th century Although originally settled by Yankees in the 1830s, the city in the 1840s had many Irish Catholics come as a result of the Great Famine. Later in the century, the railroads, stockyards, and other heavy industry of the late 19th century attracted a variety of skilled workers from Europe, especially Germans, English, Swedes, Norwegians, and Dutch. A small African-American community formed, led by activist leaders like John Jones and Mary Richardson Jones, who established Chicago as a stop on the Underground Railroad. In 1840, Chicago was the 92nd city in the United States by population. Its population grew so rapidly that 20 years later, it was the ninth city. In the pivotal year of 1848, Chicago saw the completion of the Illinois and Michigan Canal, its first steam locomotives, the introduction of steam-powered grain elevators, the arrival of the telegraph, and the founding of the Chicago Board