 While not ideal for transcontinental travel , Iowa 's dirt roads were of high quality . Foreigners even compared them to the best roads in France . However , the same could not be said when they were wet . The mud was so thick and viscous it was nicknamed " gumbo " . To show travelers the obvious benefits of paved roads , the Lincoln Highway Association began the process of creating seedling miles of paved roads . The idea , according to Henry B. Joy , then @-@ president of the Lincoln Highway Association , was to show travelers , for one mile ( 1 @.@ 6 km ) , how fast and smooth their trip could be , only to bring them back to reality at the end of the mile . Seedling miles were placed at least six miles ( 9 @.@ 7 km ) from the nearest town and in areas where the terrain was rough . Between August 1918 and June 1919 , Iowa 's first seedling mile was built in Linn County , west of Mount Vernon . The ribbon of concrete , which was 16 feet ( 4 @.@ 9 m ) wide , 7 1 ⁄ 2 inches ( 19 cm ) thick , and crowned for drainage 1 1 ⁄ 2 inches ( 3 @.@ 8 cm ) , cost nearly $ 35 @,@ 000 ( equivalent to $ 478 @,@ 000 in 2016 dollars ) to build . 
