NC 25 a long time ago 1929 Official

NC 25 becomes NC 75 1935 Gen Draft

About 1956 or 1957, NC 75 was extended east a couple blocks over what had been part of US 74-A to end at NC 200 which was using Main St at the time.
By 1962, NC 75 was extended along a rerouted NC 200 out Hayne St to US 74-601.

NC 75 initial Monroe end 1936 Union County

NC 75 extended to NC 200 1975 Union County

NC 75 extended out to US 74-601 1962 Union County

In December 1978 (NCDOT), NC 75 was truncated back to Franklin/Charlotte intersection in Monroe.
In August 2011 (NCDOT), NC 75 was supposed to have been extended north on Charlotte St and east on Church St, replacing NC 200 to NC 207. However, it appears what happened instead is that NC 75 east was truncated back to the newly designated NC 200 along Martin Luther King Jr Blvd west of Monroe. Franklin St is now SR 2100; Charlotte St is SR 1009; Church St is SR 3521.

NC 75 truncated to NC 200 Charlotte St 1982 Union County

NC 75 truncated to NC 200 west of Monroe 2017 Union County

The first NC 75 was an original state highway that began at NC 18 (or possibly at NC 17-18 jct) Lenoir. It headed east on today's US 64, then Millers Creek Rd, then US 64 again. It is unclear if NC 75 ever used Oakhill Park Rd. Once in Alexander County, NC 75 veered north on "Old NC 90" over to Ellendale.
NC 75 picked back up US 64, then used NC 90 to Taylorsville, where NC 75 likely used Main St through town. NC 75 then followed today's NC 90 through Stony Point to Statesville. It looks like NC 75 used today's US 64 through Statesville, then picked up Old Mocksville Rd over to V Point and used NC 901 east to US 64.
NC 75 then followed US 64 to Mocksville, using Wilkesboro St, Avon St, Main St and Depot St through town. NC 75 then picked up US 64 again heading east to the Yadkin River, except it used John Crotts Rd and Aubrey Merrel Rd.
NC 75 picked up "Old 64/Old Mocksville Rd" all the way to Lexington which became W. 5th St. NC 75 then cut north on Main St (was NC 10 then) and then headed east on Raleigh Rd, SR 2205. NC 75 followed SR 2205 to Randolph County, becoming Pleasant Grove Rd.
Pleasant Grove Rd criss-crosses US 64 a few times to Motleta. Then after a brief piece of US 64, NC 75 cut north on Old Lexington Rd which becomes Flinthill-Hillsville Rd, then Lexington Rd to Asheboro. NC 75 used today's NC 42 and Salisbury St over to US 64.
NC 75 followed US 64 east to Pleasant Cross Rd where 75 cut north to Franklinville. NC 75 then used today's NC 22 southeast to Ramseur. NC 75 then picked up US 64 east to Chatham County.
NC 75 picked up Graham Moore Rd and Benjie Williams Rd before settling on "Old US 64" east to Siler City where it becomes 3rd St. East of Siler City, NC 75 picked up today's US 64 to Pittsboro except for brief loops on Stage Coach Rd and Old Siler City Rd. NC 75 entered Pittsboro on US 64 Business.
NC 75 turned north on US 15-501 out of Pittsboro, then used Bynum Rd through Bynum. It appears NC 75 followed US 15-501 to NC 86 into Chapel Hill, then used Franklin St northeast. After a brief bit of US 15-501, NC 75 used Old Chapel Hill Rd into Durham. In Durham, NC 75 cut east on Morehead Ave, then Kent St, then east on Chapel Hill St. NC 75 turned north on Magnum St, then cut over to US 501 Bus on Markham Ave. NC 75 followed US 501 Business north out of Durham.
NC 75 split northeast on Old Oxford Hwy which becomes Old Route 75 in Granville County. NC 75 went through Stem and Providence, becoming today's Barnview Dr and Providence Rd. into Oxford. NC 75 used Hillboro St over to US 15. NC 75 followed US 15 to just short of Virginia where it veered northeast onto SR 1500 "Old US Hwy 15" to reach the state line, where the route continued as VA 1/VA 2.

In 1923, NC 75 was rerouted between Durham and Oxford. NC 75 moved to using Geer St away from Durham. NC 75 used Geer out to Falls Lake (no crossing today), then picked up US 15 on the other side of the lake. NC 75 then used 15 to Oxford and continued north as before. The old routing using Old Oxford Hwy has been secondary ever since.

NC 75 avoids Creedmoor 1922 Auto Trails

NC 75 embraces Creedmoor 1924 Official

In 1925, NC 75 was rerouted at Mocksville to follow NC 26 (current US 21) north to Turnersburg, using what I guess is Mount Bethel Rd and Rimrock Rd over to NC 901.
In 1926, NC 75 was changed to leave NC 26 at Dunlap, using Dunlap Gate Rd to Old Mocksville Rd over to NC 901.

NC 75 no NC 26 duplex 1923 Auto Trails

NC 75 follows NC 26 1925 Official

NC 75 adjusted again 1926 Official

About 1927, NC 75 was renumbered to NC 90 from Lenoir to Pittsboro.

Instead, NC 75 was sent south from Pittsboro, replacing NC 53 to Sanford; duplex with NC 50; replace NC 74 to Carthage; replace NC 702 to Pinehurst; duplex with NC 70 to West End; replace NC 512 to Ellerbe; replace NC 51 to Rockingham.
More specifically, NC 75 used today's US 15-501 south, then the long Old Sanford Rd, more US 15-501, Walter Bright Rd, US 15-501, then US 1 BUsiness into Sanford. NC 75 followed Carthage St to Tramway, then US 15-501 to Carthage (used Union Stage Rd, though).
NC 75 used NC 24-27 into Carthage, then NC 22 to Shady Lane Rd, then Blues Siding Rd. 75 used US 15-501 to Pinehurst except it used the Lea Rd and Campground Rd loops. At Pinehurst, NC 75 used Page Rd, then NC 2.
NC 75 followed Palmetto St straight to today's NC 5 with no zig-zag (now part of golf course), then used NC 5 northwest to current NC 211 which it followed to West End. NC 75 used NC 73 to US 220, then US 220 south. NC 75 may have used Sandy Ridge Church Rd south of Ellerbe (but stopped doing so by 1930), but used US 220 and Billy Covington Rd, then Ellerbe Rd to Five Points where it met US 74/NC 20. NC 75 may have ended there or duplexed with NC 20 east to end at US 1/NC 50 via Washington St. US 15 did make this duplex so NC 75 may have, too.
NC 75 was 100% duplexed with US 15 after this major alignment shift.
In late 1934, NC 75 was removed from US 15 from Virginia to Pinehurst; renumbered to NC 2 from Pinehurst to West End; renumbered to NC 73 from West End to Ellerbe; renumbered to US 220 from Ellerbe to Rockingham.

Hodgepodge from Pittsboro to Rockingham 1926 Official

NC 75 rerouted Pittsboro to Rockingham 1930 Official

NC 75 chopped back up 1936 Official