I've been slowly collecting bits of information about the GR&I dock on Muskegon lake for the past ten years. Found a gem today on a 1887 Sanborn map (on the Library of Congress website):
This shows a lot of detail of the freight house and dock area. The line from Grand Rapids to Muskegon was completed in 1886 so this would have all been new or repurposed from a previous operator. Prior to this the dock belonged to a manufacturing company according to an older map.
Interesting that it notes the two tracks ending at the water as "car boat dock". If I recall correctly the short lived car ferry operating out of Northport was GR&I controlled, I wonder if there were plans for one in Muskegon too.
At a later date a warehouse was added onto the freight house which extended out onto the dock, the addition is visible here:
This close up of a photo taken from a building in downtown shows the freight house with the warehouse extending out onto the dock:
PRR referred to this as the "Muskegon Wharf", it was retired from service around 1930. Would love to find out more about it, but as it is I'm always surprised to find anything at all!