One of Idaho's very first highway systems was a network of trails known as Sampson trails. Sampson trails were proposed by and named after Charles Sampson. Charles Sampson was a Boise businessman who also was a proponent of good road networks. His system of roads used a single letter designation "A, B, C, D, ..." and the Trails were marked marked with a bold black letter on an orange paint background. These routes were replaces by the more modern numbered state highway system and fell out of use in the 1930's.

Historic Sampson Trails
  Route Description Replaced By
A Boise to Wyoming via Twin Falls, Pocatello US 30, US 30N
B Boise to Canada via Lewiston, Coeur d'Alene US 30, US 30N, US 95, SH 1
C Pocatello to Montana via Idaho Falls US 91, US 191, US 20
D Boise to New Meadows via Banks became SH 15 then SH 55
E Designation Uncertain
F Boise to Blackfoot via Stanley SH 21, SH 17, US 93, SH 27
G Mountain Home to Picabo via Fairfield SH 22
H Bliss to Trude via Arco SH 24, SH 23, SH 22, SH 29, an unnumbered road
I Pioneer to Idaho Falls became an unnumbered road
J Nevada to Shoshone via Twin Falls US 93
K Utah to McCammon via Preston US 91
L Designation Uncertain
M Washington to Montana via Coeur d'Alene became US 10 then I-90
N Bonners Ferry to Montana US 2
O Oregon to Caldwell SH 49, SH 18
P Utah to Downey SH 36
Q Declo to Fairfield SH-25, SH-46
R Designation Uncertain
S Oregon to Nampa SH-45, an unnumbered road
T Star to Grimes Pass SH-16, unnumbered road, SH-17
U Utah to Montpelier SH 35
V Utah to Montpelier US 89
W Designation Uncertain
X Designation Uncertain
Y Bonners Ferry to Canada US 95
Z Designation Uncertain

Related Pages
 Idaho Highway History
 Idaho Home Page
 Sampson Trails
 Sampson Trails @Wikipedia