The modern-day Jefferson Highway Association, dedicated to promoting the 1910s north-south Pine to Palm Highway, is having its 2017 convention in Denison, Texas. The JH ran through Iowa mostly on now-US 65 and 69, sharing the Lincoln Highway in Story County. Here is a Google map of the entire route but I think the Iowa routing needs to be refined.
The Lincoln Highway Association, meanwhile, is having its annual convention in Denison, Iowa.
Now that is a coincidence.
(I know what the secret museum on the LHA agenda is!)
(WHAT DO YOU MEAN THE BUS LEAVES AT SEVEN AM)