While there are lots of inputs that effect how good a crop you will be able to produce in a particular location or a particular year, a very important factor is water (especially rain). While today lack of rain can be mitigated to some extent through irrigation systems, in the 19th century crops lived or died according to the rain and a single bad year could wipe out a farm that wasn’t prepared for it. (During the late 20th century there was a circular irrigation system on the Ingalls Homestead and you can still see some signs where all the extra water over the years has made a difference and creates a slightly greener circle where it once was located.)
People often think of the Midwest as uniform, but there are actually a lot of different geographic and climate zones across the area generically known as the Midwest. Iowa is thought of as having some of the best climate and soil for agriculture (which it does) and it also has a good amount of rain (when not in drought conditions). On average, and in Iowa’s case by average we mean typical, eastern Iowa (specifically Dubuque located on Iowa’s eastern border right on the Mississippi River) has just over 35.5 inches of precipitation a year. West of the Mississippi the amount begins to slowly drop but still holds to 34.72 inches by the middle of the state (specifically Des Moines) and has dropped quite a bit to 25.99 almost 10 inches difference by the time you reach the western part of the state (specifically Sioux City). Just jump over the Missouri River to the opposite shore and the rate of decrease speeds up. Eastern South Dakota gets between 24 and 27 inches, central South Dakota gets 17 to 20 inches and western South Dakota gets less than 17. Remember in good climate eastern Iowa the number was over 35 inches, twice what western South Dakota gets. In addition South Dakota precipitation rates are much more volatile than Iowa. By average, they mean the mathematical average as the weather vacillates between flood years (which they had a couple of years ago) that fills all the prairie pothole lakes like Silver Lake and drought. Usually in the wet years they can make enough to get through the dry if farmers realize they are coming.
The years Laura Ingalls Wilder describes in her last few books tended towards the wet. In fact, the railroads trumpeted a man whose “scientific” theory was that plowing released moisture in the soil and permanently altered the climate for the better and many people believed that was what was happening. Farmers who believed that and over expanded on the belief the wet years they came were typical found themselves in debt with land that wouldn’t produce when the drought cycle . The drought cycle did come again which explains some of the crop problems Laura and Almanzo had in the early years of their marriage. The National Weather Service says De Smet, South Dakota gets an average of 24 inches of rainfall annually.
Read more about the myth of “rain follows the plow” here:
Last Updated Aug 8 2016: I updated to my current signature block, but otherwise I think it’s still good. I took a couple of references to recent weather out.
Sarah S. Uthoff is the main force behind Trundlebed Tales striving to bring the History, Mystery, Magic and Imagination of Laura Ingalls Wilder and other greats of children’s literature and history to life for a new generation. Uthoff is a nationally known Laura Ingalls Wilder authority and has presented at five of the Wilder homesites, many conferences and numerous libraries, museums, and events around the Midwest. Attend one of her programs, schedule one yourself, watch her videos, listen to her podcast, and find her onFacebook, Twitter, Google+, LinkedIn, and Academia.edu. Professionally she is a reference librarian at Kirkwood Community College and director of the Oxford (Iowa) Public Library.