The people of the Dust Bowl blamed the causes of a multiple of things.  At the time though many were unsure of what actually was the cause.  Scientists have studied this event for several years before determining several causes.
The main cause of the Dust Bowl was due to a massive drought in the Great Plains of the United States during the 1930s, or the "Dirty Thirties".  There have been many studies done as to why the drought lasted so long but no direct cause has been found.  There are several correlations between slowly varying Pacific Ocean sea surface temperatures and precipitation in the United States.
When settlers of the Great Plains first arrived the Great Plains were just grassland.  Over time these settlers transformed this area to farmland.  With the turn of the century and new technology to make farming easier, most of the land was now devouted to the use of crop production.  During the drought, the soil dried out, became dust, and blew away eastwards, mostly in large black clouds. At times, the clouds blackened the sky all the way to Chicago, and much of the soil was completely lost into the Atlantic Ocean.

On November 11, 1933, a very strong dust storm stripped topsoil from desiccated South Dakota farmlands in just one of a series of bad dust storms that year. Then on May 11, 1934, a strong two-day dust storm removed massive amounts of Great Plains topsoil in one of the worst such storms of the Dust Bowl. The dust clouds blew all the way to Chicago where filth fell like snow, dumping the equivalent of four pounds of debris per person on the city. Several days later, the same storm reached cities in the east, such as Buffalo, Boston, New York City, and Washington D.C. That winter, red snow fell on New England.

On April 14, 1935, known as "Black Sunday", twenty of the worst "Black Blizzards" occurred throughout the Dust Bowl, causing extensive damage, turning the day to night. Witnesses reported that they could not see five feet in front of them at certain points.