8 P of E (LJS) 7 E of a FPP 18 VA 60 S in the USA 24 B (B in a P) 2 W in a F 7 C of the W 22 B on a ST 70 TSY and T 568 M in a P 32 T in an AM ? YIWB 44 M (H of NC) 206 B in a HS
Bridgenut, TeeGee, cruciverbali (there's posh), swannbaker, FoxLee, prstanway - your speed of answering is amazing. prstanway - Nelson's column is 44 metres high and the speed limit in USA is 60, but I think the ditloid should include the L for limit, so still unsure whether to go for the speed limit or the 50 states and assume the compiler made a typo.
I don't know how you can say the speed limit in the US. is 60. I googled it - they have about 6 different types of road and each one carries its own speed limits, e.g. 25-30. Not even a definitive number. And each state can set its own speed limits. As you say, it would have had an 'L' in the clue anyway.