In this episode, Matthew and Ingrid just "met" for the first time. In earlier episodes they talked to each other. He even had her over for dinner, where they learned that Ingrid and the others were starving. This episode was aired out of order and is indeed the first time Ingrid and Matthew meet.
When Miss Olive took the immigrant girls to the Mercantile for cloth for dresses, she explicitly directed the girls not to select red cloth. As the girls gather for the final prep before the dance, one of the immigrant girls is wearing a red dress.
Loren shares that he met Maude at a dance and fell in love. In season 2 Miss Dorothy reveals that Loren proposed to her first.
Horace's saying that Custer isn't a real general is actually correct in that his post-Civil War rank in the West was Lt Col. During the Civil War he was given the brevet (temporary) rank of General in the Voluntary Army, but after the Civil War he was discharged into the regular cavalry.
A hurdy-gurdy is a mechanical violin that is cranked. No one is playing one in this show. Hurdy Gurdy Girls was a name given to loose women who were either sold or used to make money in frontier dance halls in the 1860s.
It is a well documented fact that Custer preferred to wear the fringed buckskins of a frontiersman while out West. The actor is only seen in Cavalry uniform with nontraditional hat.
Chad Allen can be seen wearing a pair of blue pants with belt loops. Belt loops weren't invented until 1922.
Loren can be seen using a modern style fly swatter that was not invented until 1900.