Shelter 1 was located on a flat plain the mountains. A river flowed through this plain. So there were way more troops and civilians stationed in this shelter. Basically all the civilians that survived in the surrounding cities had gathered here. The population approximated two millions, crowding this spacious plain.
The United States was one of the leading countries prior to the catastrophe of Transformers. Despite 99% of its cities were destroyed, the reserve stockpiled by the federal government and those remained in the smaller cities and towns could feed several million people for a period of time.
