Don't know how it's signed now, but you'll come across the point near I-44 where US 59, US 60, US 66, and US 69 came together briefly.
Also, at the southern split of US 69 and ALT US 69 (Historic 66), there is a big yellow sign warning truckers not to take main US 69 but to take ALT 69 instead. If you're curious, look at Google Street View's version of why instead of you taking a side trip up to the towns of Picher, OK and cross-border companion Treece, KS. They are EPA superfund sites. A local lead mine operated there for decades, but excavated too close to the surface. There have been several sudden sinkholes since. Also. the mine operations polluted the town's groundwater. You will also see several piles of dirt off in the distance. These are also remnants of the mining. The dirt in the piles has traces of lead, and when the wind blows it takes the lead particles with the dust. If that's not bad enough, Picher got hit by a tornado a few years ago, damaging what wasn't already messed up by the lead mine.