when was the new 4 lane hiway 75 in grayson county (Sherman) texas completed?

Question

I was told hiway 75 was completed from Oklahoma to Dallas texas by 1956. I can not remember the new Hiway 4 lane completed then

Answer 1

According to this http://tuibguy.messagemonster.com/
in the 70's.

Answer 2

the last bit between mile marker 56 and 52 was finished up about 99 i think, I used to have to drive it every day