Fort Wallace (where Matt and Sarah are going) was actually a real US Fort from 1865-1882. All that remains of the old fort is the Fort Wallace cemetery.
Matt calls the meal he and Sarah are eating "son-of-a-gun" stew. That's the polite term. It was commonly called "son-of-a-bitch" stew. It was basically "chopped calf", including the calf's marrow gut.
The title is based on the 1913 song "There's a Long, Long Trail" by Stoddard King and was very popular during World War I with soldiers and at the home front.
There is a museum at Fort Wallace. It can be seen at Google maps, along with pictures of the cemetery.