the scent of country highways in MO

This is silly, but:
i am a St. Louisan transplanted (though not setting new roots well) to the east coast.
Last year i started a garden.
The one thing i REALLY wanted to grow was sweetgrass. I was convinced that the scent i loved growing up driving out the highways was sweetgrass. I don't like fragrant flowers, but this i love.
But, of course, i could find none anywhere. At the end of last season, someone finally turned me onto sweet woodruff, which smelled kinda like it, but it all died. (and it's supposed to be problematically invasive - go figure...)
Now, i was reading that sweetgrass isn't usually found in MO, and that it only smells after it is dried.
So WHAT is that sweet smell of summer that i remember from trips to Six Flags and Hannibal? It must be something that grows naturally - and be pretty common. sweetgrass? vanilla grass? woodruff? some kind of hay? (when i was a kid we said it smelled like silly putty - or at least the kind we had in the 70s.)
I know I can't expect a precise answer, but...
any ideas???

thanks...

amy
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What time of year do you remember smelling it? Dames Rocket is very fragrant. It has large purple flower heads and grows all over. It usually blooms here during the spring and early summer.