 As a result, 405 is the only area code in the state that does not reach the state's borders with Arkansas, Missouri, Kansas, Colorado, New Mexico, and Texas.Despite the rapid growth of the Oklahoma City metro area and the proliferation of auxiliary devices (cell phones and pagers), as of October 2017, 405 is projected to likely remain in its current configuration until at least the second quarter of 2021, at which time a split or overlay of 405 may be necessary.An overlay of 405 has been recommended.