A rambling note about wheat.
Perhaps Randy can tell us more from the historic farm, but to the best of my knowledge wheat was shipped in sacks through the 19th century and well into the 20th century.
Before the development of the internal combustion engine, threshing machines were parked in the middle of a field and made to function with a stationary tractor (often steam, later gasoline) connected to the thresher with a big leather belt. Then, wheat was cut (often enough by hand), shocked, and carried in wagons to the thresher. The wheat was sacked at the machine – and stayed sacked until it reached the flour mill. The internal combustion engine led to the development of a mobile combination cutting and threshing machine (the "combine"). Even with its own motor, the combine was pulled around the field with horses or later with a tractor. The combine had an auger which allowed the wheat to be offloaded loose – in bulk – to the great relief of man's back. Long before I started cutting wheat – while I was in grad school – the combines were self propelled. We never stopped from about 11 am (when the humidity dropped) until midnight (when the humidity rose and the straw got too tough to cut). As late as the late 1950s Kansas farmers were harvesting 10-15 bushels per acre. In the 1980s when I was at it, we often cut 50-60 bushels per acre. The difference was chemical ferterlizer. The funny thing, even with inflation, the price paid for bushel in the 1980s was about the same as during WWI. Back then wheat would support a family on as little as a quarter section (section = 1 square mile). My uncle's family was cutting 7 sections – and probably were only still in business because of the oil wells.
The change over from sacked to bulk must have begun about WWI--during which time my dad nearly suffocated in bulk wheat in a grain elevator. But the change from sacked to bulk may not have happened all at once. It was not until the 30s that the tractor began to change the farm economy in a big way. Then the tractor enabled the landowing farmer to farm all of his land himself or with a few hired men – and the sharecropper method came to an end. (The Okies who went to California were displaced sharecroppers – the Dust Bowl had nothing to do with it – the Dust Bowl was western Kansas and Oklahoma while the displaced "Okies" were from eastern Oklahoma.)
One other change between 1900 and today is the height of the plant. Now days wheat is bred to be shorter than when it was cut and tied into shocks. Farmers don't like to have all that straw to handle.
Now, I know there were loading marking and grain doors in boxcars. I have always assumed this referred to bulk loading, and thus would have dated fairly early. But now that I think about it, perhaps those load marks and even the grain doors went along with sacked wheat as well. I thank God I never had to move sacked wheat.