NC 691: was born in 1925 as new routing. It ran as a short connector between NC 69 (current US 19E) Ingalls east to NC 194 (current US 221 and "old NC 105" jct) near Linville Falls.
In 1926, NC 691 east was truncated to NC 194 near Altamont as NC 194 was rerouted over the N-S portion of NC 691.

NC 691 initial route

NC 691 moved northward

In 1930, NC 691 was extended northeast to end at US 21/NC 26 near Sparta. This was accomplished by:
Duplex with NC 194 to the Crossnore area
Replaced NC 181 from NC 194 to Pineola
Replaced NC 176 from Pineola to Linville
Replaced NC 175 from Linville to Blowing Rock
Replaced or duplexed (unclear) NC 17 from Blowing Rock to Boone
Replaced NC 69 from Boone through Jefferson to US 21

In conjunction with this big expansion of NC 691 from 4 to 97 miles, US 221 was assigned to the entirety of NC 691.

Pre-691 expansion

NC 691 expansion

In 1932, NC 691 was reduced back to the 4 miles between US 19E/NC 69 and US 221 Altamont, replaced by an expanded NC 28 as well as US 221 remaining. Today it is still mostly US 221 except Boone to Jefferson is now NC 194.

In 1933, NC 691 became part of NC 194 which it remains today.

Post-691 expansion

NC 691 expansion