It had the same extent it does today; only slight modifications have been made to its alignment due to the straightening of connecting highways.

[3] As of 2012, the highest average annual daily traffic (AADT) count along SH-108 was 5,900, measured along the concurrency with SH-51.

[2] The highway was mostly gravel at that time; only the portions from the southern terminus to Ripley and the concurrency with SH-51 were paved.

[8] In 1963, the paved segment extended north of Glencoe, to the highway's northern terminus.

[9] The first change to the highway's alignment occurred on November 1, 1966, when SH-51 was straightened between Stillwater and Yale; SH-108 was realigned to continue to concur with SH-51.

[a] The final change to SH-108 was made on June 4, 1974, when a straightening of SH-33 resulted in a slight extension of SH-108 to continue to meet the new highway.