Designation, configuration, and higher headquarters assignment are the most recent ones prior to U.S. entry into World War II • 1st Engineer Regiment (
1st Division - 1st Battalion redesignated 1st Engineer Battalion (Combat) on 12 October 1939 and regiment disbanded on 16 October 1939 • 2nd Engineer Regiment (
2nd Division - 1st Battalion redesignated 2nd Engineer Battalion (Combat) on 12 October 1939 and regiment disbanded on 16 October 1939 • 3rd Engineer Regiment (
Hawaiian Division - Regiment reorganized and redesignated 3rd Engineer Battalion (Combat) on 26 September 1941 and assigned to the
24th Infantry Division • 4th Engineer Regiment (
4th Division - Regiment reorganized and redesignated 4th Engineer Battalion (Combat) on 19 October 1939 • 5th Engineer Regiment (
II Corps) • 6th Engineer Regiment (
3rd Division) - 1st Battalion redesignated 6th Engineer Battalion (Combat) 12 October 1939, 2nd Battalion redesignated 10th Engineer Battalion (Combat) 13 October 1939 and relieved from the 3rd Division, and remainder of regiment disbanded • 7th Engineer Regiment (
5th Division) - Regiment reorganized and redesignated as the 7th Engineer Battalion (Combat) 16 October 1939 • 10th Engineer Regiment (
8th Division) - Disbanded 14 October 1939 • 11th Engineer Regiment (
Panama Canal Division) • 14th Engineer Regiment (PS) (
Philippine Division) • 15th Engineer Regiment (
9th Division - Regiment reorganized and redesignated 1 July 1940 as the 15th Engineer Battalion (Combat) • 16th Engineer Regiment (
1st Armored Division) - Withdrawn from the Panama Canal Department 15 July 1940. Concurrently, reorganized and redesignated as the 16th Engineer Battalion (Armored), assigned to the 1st Armored Division, and activated at
Fort Knox,
Kentucky, from personnel and assets of the 47th Engineer Troop (Mechanized). • 18th Engineer Regiment (
IX Corps) • 19th Engineer Regiment (
III Corps) • 20th Engineer Regiment (
IV Corps) • 21st Engineer Regiment (General Headquarters Air Force) - Redesignated 4 June 1940 as the 21st Engineer Regiment (Aviation), relieved from the IV Corps, and assigned to the General Headquarters Air Force. • 22nd Engineer Regiment (General Service) (III Corps) - Redesignated 22nd Engineer Battalion (Armored) 28 August 1941 and assigned to the
5th Armored Division • 23rd Engineer Regiment (General Service) (
VIII Corps) - Redesignated 23rd Engineer Battalion (Armored) 28 August 1941 and assigned to the
3rd Armored Division • 24th Engineer Regiment (General Service) (
VI Corps) - Redesignated as the 24th Engineer Battalion (Armored) 16 December 1940 and assigned to the
4th Armored Division • 25th Engineer Regiment (General Service) (
VII Corps) - Redesignated as the 25th Engineer Battalion (Armored) 28 August 1941 and assigned to the
6th Armored Division • 26th Engineer Regiment (General Service) (IX Corps) - Inactive; disbanded 22 December 1942 • 34th Engineer Regiment (Combat) (General Headquarters Reserve) • 35th Engineer Regiment (Combat) (
First Army) • 36th Engineer Regiment (Combat) (First Army) • 37th Engineer Regiment (Combat) (VIII Corps) • 38th Engineer Regiment (Combat) (
I Corps) • 39th Engineer Regiment (Combat) (
Second Army) - Redesignated 19th Engineer Regiment (Combat) 1 July 1940 • 41st Engineer General Service Regiment (Colored) (First Army) - to Liberia as part of U.S. Army Forces in Liberia under
United States Army Forces in the Middle East. • 42nd Engineer General Service Regiment (Third Army) - Redesignated 20th Engineer Regiment (Combat) 1 July 1940 • 43rd Engineer General Service Regiment (Second Army) • 44th Engineer General Service Regiment (First Army) • 45th Engineer General Service Regiment (Colored) (Third Army) •
46th Engineer General Service Regiment (Third Army) • 47th Engineer General Service Regiment (Fourth Army) • 78th Engineer Regiment (Combat) • 101st Engineer Regiment (Combat) -
26th Division • 102nd Engineer Regiment (Combat) -
27th Division • 103rd Engineer Regiment (Combat) -
28th Division • 104th Engineer Regiment (Combat) -
44th Division • 105th Engineer Regiment (Combat) -
30th Division • 106th Engineer Regiment (Combat) -
31st Division • 107th Engineer Regiment (Combat) -
32nd Division • 108th Engineer Regiment (Combat) -
33rd Division • 109th Engineer Regiment (Combat) -
34th Division •
110th Engineer Regiment (Combat) -
35th Division • 111th Engineer Regiment (Combat) -
36th Division • 112th Engineer Regiment (Combat) -
37th Division • 113th Engineer Regiment (Combat) -
38th Division • 115th Engineer Regiment (Combat) -
40th Division) • 116th Engineer Regiment (Combat) -
41st Division • 118th Engineer Regiment (Combat) -
43rd Division • 120th Engineer Regiment (Combat) -
45th Division • 121st Engineer Regiment (Combat) -
29th Division ==Regiments formed during wartime==