SOLVED. detective western where 2 brothers (Swedish?) get hired as railroad detectives (even though they loathe the RRs). The inventor of peanut butter is on board (w/ a lot of humour!) [s]

[MentorsAcrossAmerica.com]

I'm looking for a detective western (w/ a lot of humour) where 2 brothers (Swedish?) get hired as railroad detectives (even though they loathe the RRs).
The inventor of peanut butter is on board
(& the oily, disgusting mess it originally was)
is humorously referenced a few times within.

[Kris]

On the Wrong Track by Steve Hockensmith seems to match your description.

[Summer]

This is absolutely On The Wrong Track. It's a great book.
The protagonist and his brother are redheaded German-American cowboys. Otto is a writer, and his older brother Gustav wants to be a detective. They are hired as railroad detectives, but hate the railroad companies. They see peanut butter for the first time, since a traveling salesman is bringing jars of it back from the World's Fair, and they don't like it.

[Lobstergirl, au gratin]

OP seems absent. Moving to Solved.