I have been asked by our E-911 people to find feature classes for railroad crossings and mile markers attributed with their official number designations. My co-worker stumbled upon an ArcGIS Online app that show this, but we couldn't actually download the data. I believe the app was from the My County group.
I got my mile posts from the state department of transportation. Can't remember where I got the railroad crossings. Maybe the Federal Railway Administration. Or maybe it was dot as well.
I was able to find Rail Roads at my state DOT and my state DNR websites