What's with the red 55mph on the speedo?

55 used to be the interstate speedlimit way back when. i remember back in the 80when 55 was the speedlimit and when it got bumped to 60 and then 65 it was like WOW. now everywhere around me is 70-75 depending on which state you go into.
 
Correct. 55mph used to be the typical speed limit so they marked it for quick reference. Since 55 isn't the typical speed anymore, you don't see that on many cars nowadays.