I don't know the intended route of the proposed railroad. It could have been that it arced into Dallas County, but I assumed it was to follow the Chicot Trace which I believe went through Calhoun County. I am attaching a link to a website that John Brown's GGGrandson put together of his Diary. It is a very interesting and tragic read for Civil War buffs and records a lot of mundane information that isn't covered in history books. His grandson also included information about Brown's daughther who suffered from mental illness and had been redacted out of earlier typed copies of the diary.

I don't recall if the name of the railroad is mentioned, but if it is, it might give you some clues about where to start your research. There may be old right-of-way documents in state archives.

Here is the link: http://web.mac.com/paulswepston/JohnBrownDiary/Welcome.html

I grew up in the corner of Calhoun County and I am always interested in local stories. Who was the soldier you are reading? Is it a published book or private works you are reading?