The 40th annual Gaithersburg, Md. railroadiana show will be held on Sun, Nov. 5, 2017 at the Montgomery County Fairgrounds. Early admission for Fri. Nov. 3 and Sat. Nov. 4 is also available. There is also a toy train show at the same location on Sunday Nov. 5.
One admission is good for both the railroadiana and the toy train parts of the show. More information can be found here.
http://www.gserr.com/shows.htm
Check this link for pictures from past shows here. Always something interesting to see.