Show longest american tunnel the cascade railroad ralli oad tu tunnel tinel longest on the american continent Is miles in length it was built through 11 solid granite and Is lined throughout hout with concrete conci ete tile hie tunnel Is straight ns as it a rifle ride bore but the eastern portal la Is WA feet higher thon than the western this gives a continual how flow of fresh air through the tube aik oik was as commenced december Decem lier 23 28 1025 1925 and the ille tunnel was completed ready for track t r ack laying december 25 1023 |