The steel works probably provided steel for additional rail but more likely material for Omaha and probably surrounding areas like Lincoln. Supposedly being the largest iron smelter in the world at the time, it is even vary likely that it received and shipped materials and product from/to places very far away. Taken in 1938, the image shows the factory during the Great Depression. This was probably a source of many jobs for the region, although I wouldn't be surprised if they had experienced their own amount of layoffs due to decreasing business (although it was possibly revitalized during the public work programs being a producer of building materials). That means that these grounds were full of not only the imagined image of the typical factory worker (poor, likely uneducated, even carrying connotations of dirty, rough, etc) but also others not typically factory workers but that had fallen on hard times like the many others, taking what they could get.
An interesting note, probably resulting from coincidence instead of planning or actual lack, the are no people visible in the picture, or cars, or anything non-industrial (the background/horizon being faded enough to make indiscernible). There aren't even any plants that can be identified in the image. The lack of anything organic makes the image appear more stark, emphasizing its industrial nature. This, when matched with the smoke and fading of the distance and the fact that the picture is black and white (just due to the technology of the time), create a sense about as far away from natural as you can get. Accompanying all our sense of the Great Depression as a whole along with ideas about factories (especially during times closer to the industrial era), the picture's elements also give a sense of drudgery/a place that you don't really want to be but may have to.