All across the country during the 1930s, many new US routes were created and several existing US routes were extended. If during that timeframe Oklahoma had tried to address their concerns by getting one or two new north-south routes, they probably would have been successful. But for whatever reason, it appears they did not make an attempt during those early years. Already by the 1940s AASHO had become much more particular about new additions to the US route system. And it wasn't until 1952 that Oklahoma started trying to extend some north-south US routes through the central part of the state. That was the year when Oklahoma proposed extending the US 377 designation along the corridor shown in green on this map:
I have not seen any documents stating why AASHO denied that proposal, but I will suggest a couple possible reasons:
...one of the reasons I suspect Oklahoma did not seek buy-in from Texas is that, just four months later, they submitted another request to AASHO. This proposed route was nearly identical to the first one, except this time Oklahoma addressed both of the issues above: it was the US 177 designation (instead of US 377) that they proposed extending, and the south terminus would have been at US 70 in Dickson, so there was no need for cooperation with any other state:
I do not know why AASHO rejected that proposal (nor what changes may have taken place between then and 1965, at which time AASHO changed their position and did approve that extension of US 177, as we will see below). At any rate, the following year (1953), Oklahoma proposed extending US 377 again, but this was along a different corridor running all the way between the north and south state lines:
On the map above, that route would have followed the red and purple segments. But again, to make the south end of that idea work, Texas would have had to extend US 377. And on the north end, AASHO probably would not have allowed a US route to end at a state line, but to my knowledge Kansas had no interest in the US 377 designation.
I believe Oklahoma's main goal with these proposed extensions of US 377 was to have a US route serving Ada. After a few rejections, the next approach they tried was to extend the US 169 designation south from Glenpool (outside Tulsa):
That route would have followed the blue and purple segments on the map above. Over 80 miles would have been concurrent with US 75, and within that stretch there also would have been a 20-mile triple-overlap with US 62. Perhaps that is why the proposal was rejected; at any rate the following year Oklahoma tried again...
...and was rewarded with another rejection. Their next US 169 entry, from the following year, is interesting and perplexing:
The entire stretch from Glenpool to Henryetta was already essentially served by US 75, and the segment between Okmulgee and Henryetta additionally carried the US 62 designation. So why did Oklahoma want US 169 to be overlapped along that route? And why did AASHO agree to it? In fact, did they actually agree to it?
Regarding the reason why Oklahoma wanted to extend US 169 to Henryetta: this is just a theory, but in 1959 the road that would eventually become the Indian Nation Turnpike was at least proposed, if not already under construction south of Henryetta. It is possible that Oklahoma was originally planning to extend the US 169 designation along that road.
If so, then why might they have signposted the extension absent AASHO's approval? In light of all the rejected proposals earlier that decade, Oklahoma might have determined that they could not count on AASHO to support their plans.
To be clear, I have no evidence that AASHO did not approve of the extension, but considering their previous disapprovals it would be surprising if they allowed it. Moreover, I have never seen any map -- not even an official OKDoT map -- that shows a US 169 marker south of Glenpool... as if they were trying to keep it secret.
At any rate, I am quite certain that Oklahoma signed US 169 down to Henryetta, because a few years later they truncated the designation back to Tulsa...
...and I have seen documents instructing crews to remove US 169 signs between there and Henryetta. But what was the reason for this odd truncation that came only a few years after the extension? I can offer only theories:
At this point we will backtrack a few months and note that AASHO actually did approve one of Oklahoma's proposed extensions:
Ignoring the misspelling of Dickson, that was identical to the 1952 proposal. It is unknown what happened during that 13-year interval that prompted AASHO to relent and approve the same application that they had previously denied. The remainder of US 177's history in Oklahoma can be found on the main US 177 page.
Now we will backtrack one more year to view another of Oklahoma's proposals to extend US 377:
That was the same as the 1953 proposal, except instead of going all the way up to Kansas, US 377 would have ended at its junction with US 64 near Cleveland. It is unclear why Oklahoma decided not to include in their proposed extension the segment of OK 99 between Cleveland and the junction with US 60 in Pawhuska. But the question is academic, because this proposal was denied. At that time, Texas has still not extended US 377 north of Denton. But that finally happened four years later, when AASHO approved an extension of US 377 from Denton to Madill:
At first glance, that might seem like a small victory for Oklahoma. However, when one looks at what they actually requested from AASHO, and compares that to what AASHO approved, it seems quite possible that Oklahoma viewed it as more of an insult. The image below is from the meeting minutes of AASHO's Special Committee on Route Numbering. It shows the proposal that was submitted, along with a decision regarding which segment of the extension was approved:
This suggests the possibility that Oklahoma did not immediately sign US 377 in their state; they may have been waiting until their full request was approved. At any rate, Oklahoma did not waste time applying for permission to extend the US 377 designation further north from Madill. Again. And again. And again... multiple times over the next 10+ years:
Why did AASHO (AASHTO as of 1973) keep denying Oklahoma's request? I have seen a few OKDoT documents related to this: one stated that an extension was not approved because the road in question needed improvements in order to be considered compliant with standards for a primary route. But another stated that the amount of US routes in that part of Oklahoma was too dense. Whatever the reasons might have been, why did Oklahoma keep submitting the same request, over and over? Had they been making changes to the road that they expected would cause AASHO to change their answer? Something finally prompted them to stop asking after 1980 -- presumably the realization that nothing was going to make a difference with AASHTO. It is unknown what (if anything) happened with this situation over the next 7-8 years. But what Oklahoma did in 1988 was almost* without precedent: they unilaterally decided to extend a US route without AASHTO approval. The following is a line from their highway revision list for US 377:
That 120-mile extension of US 377 is without a doubt the single most blatant example of an AASHTO policy violation. And it is not a good precedent: the uniformity and integrity of the US route system depends on the voluntary cooperation of the state highway departments. But with that said -- after reading the long history of Oklahoma's multiple requests and AASHTO's chronic denials -- one can easily see why Oklahoma decided to go rogue and signpost the route without approval. The north end of US 377 (at least according to Oklahoma) is still in Stroud; photos from there can be viewed on the main US 377 page.