When the current K-10 expressway was originally completed between K-7 and I-435, it was originally signed as K-12. When the entire expressway was completed from Lawrence to I-435 in Lenexa, K-10 was signed for the entire freeway, and K-12 was realigned to follow the old K-10 routing on Shawnee Mission Parkway to Merriam Drive. The former Spur K-10 was then resigned as Spur K-12.
The original K-10 expressway was initially designated as K-12, but later became K-10 when it was extended from K-7 to I-435 in Lenexa. The former Spur K-10 was then reassigned as Spur K-12.