Essentially a Grain Warehouse but now with an integrated Grain Elevator mechanism. Some of this type were built integrated as new buildings, and some were the result of an addition to a pre-existing warehouse
A recent trend may be back towards this building type, with sprawling single-level pole barn/warhouse-like buildings - perhaps "Elevator Warehouses."
(Images borrowed from the I&M Canal Corridor Association)
These images (two versions of the same photo) are of one of the first "Incipient" Grain Elevator, built in load-bearing stone in 1848. Hiram Norton's facility built on the Illinois & Michigan Canal near Chicago helped change the tide of the grain industry. His was a flat-roofed, 3.5 story stone warehouse-looking building. It actually looks more like the Steel-Frame grain elevators - which post-date it by 30-40 years. An office wing was an early addition.
Loading grain at the Norton Building 1870. This photo taken in 1870 shows the Norton Building in Lockport. The photo shows a grain boat being unloaded at the Norton & Company canal warehouse. This building still exists and is used for commercial purposes. Note that the boats had big long decks with hatches. Grain was loaded and unloaded mechanically. This was an innovation that came in with the canal in 1848, that of hauling grain in bulk rather than in sacks. (I&M Canal History: Photo Vault)
Both warehouse and office wing still stand.
In the center of the photo is another early, smaller Grain Warehouse with Elevator, built only two blocks away on the same Illinois & Michigan Canal. It was originally an ordinary warehouse built in 1838 by the canal builder, who later sold it. I presume the front (left) part was a residence or office since it had/has a two-tier porch facing the canal. Other later Grain Elevators clutter the skyline in the background.
The warehouse was modified sometime probably between 1848 and 1853 with the addition of the headhouse and Grain Elevator, and arched wagon doorways cut into the side walls. In 1859, the three-story office/commercial part was added, like on the Norton Building.
After being further altered into almost unrecognizability, the three parts were restored/renovated in the mid-1980s into what is apparently a vibrant part of the I&M Canal Corridor Association.