I live in Omaha...I also have a Lowry connection through Elijah Malachi Lowry of Henry County, Tenn. Don't know if I'm at all related to James Lowry, but it got my curiosity up when I saw the name in your posting.
I'm quite familiar with the stockyards...they just remodeled the old stockyard building and it is now a mixture of office, residential and entertainment space. They did a good job preserving history. I'll do some research on the Delmonico...I'll contact a history professor at UNO who is very involved in Omaha's history. He might have some good pointers in obtaining information, especially in regard to advertising which is something he particularly cares about. I'll also scout the area and if I locate the building I'll snap a picture and send it on. Let me know if you have any more details. I find this type of research very interesting.