Middle name comes from 1917 Draft List at Dawson County, NEGenWeb Project.1866

1920 Census, Eddyville, Dawson Co., NE
Grim, Carl F., head, 30, b. NE, farm operator
Edith, wife, 28, b. NE
Elgas, son, 6, b. NE

In the 1919 Platbook of Lincoln & Hillside Precincts, Dawson Co., NE is listed:
Grim, Carl F. Wf. Edith; ch. Elgas. P. O. Lexington, Star Route. O. 159 ac., sec. 26. (29.)

Carl’s last residence was South Pasadena, Los Angeles Co., CA; his Social Security number was issued in Nebraska.8

Carl did not have a middle name, only a middle initial, in spite of some sources which record a middle name, according to his niece, Polly Munson Cronin.1537

Obituary, Lexington (Nebraska) Clipper, May 3, 1984 (found on FindaGrave.com)
“Carl F. Grim Died in California Memorial Services Here
Carl F. Grim, 94, of Pasadena, Calif., formerly of Lexington, died Thursday, at Pasadena where he had made his home the past few years.
Memorial services will be conducted Saturday, June 2, at the First Christian Church in Lexington with the Rev. George Keebler officiating.
He was born Dec. 13, 1889 at Overton and had been a resident of the Overton and Lexington communities all of his life until moving to California about four years ago to be near his son and family.
He is survived by his daughter-in-law, Mrs. Elgas Grim of Pasadena and grandchildren.