It's 1967 and you're cruising down a Montana highway on a sunny
afternoon in your new red mustang GT with a 325 h.p. V8.  How fast can
you drive without breaking the law?

Hello.

Before 1974, Montana's daytime highway speed limit was a "reasonable
and prudent speed" (i.e., there was no numerical speed limit).
 
Thus, in 1967, if you were cruising down a Montana highway on a sunny
afternoon, you could drive as fast as would be "reasonable and
prudent." There would not have been a specific speed limit.


sources: 
 
"In 1996, the State of Montana reverted to the state speed limit
policies that existed prior to 1974 and the National Maximum Speed
Limit. The National Maximum Speed Limit was repealed in December of
1995. Montana returned to the use of Reasonable and Prudent speed
limits on its federal and state highways."
source: Motorists.com: 
http://www.motorists.com/pressreleases/montana.html  

'Montana reinstated the pre-1974 daytime limits of "reasonable and
prudent" and 65 mph at night.'
source: Chronicle ADTSEA 
http://www.adtsea.iup.edu/adtsea/TheChronicle/summer_96/can_state_lawmakers.htm
 
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search strategy: 
montana "speed limit" 
montana "speed limit", 1974 
montana "speed limit", reasonable, prudent 
 
I hope this helps.

zenny1212-ga