Unlike joining other factions in Fallout 4, joining the Railroad faction actually requires some grinding.
How to Join The Railroad Faction
In order to join this faction, firstly, you need to find all the clues leading to finding out about the faction’s hidden headquarters.
Once you have done that, you will be required to complete Road to Freedom mission. Once you have successfully done it all, you’ll be able to join the Railroad faction and complete optional missions offered by the faction.
Similar to other three factions in the game, you’ll be able to complete missions as long as you wish, however, do note that doing so will negatively affect your relationships with other three factions namely the Institute, the Brotherhood of Steel, and the Minutemen in the game.
This is all you need to know in order to understand how to join the Railroad faction. If there is something else you would like to know, make sure to let us know in the comments section below!