1920 U.S. Census, Baltimore City, Maryland
6th Ward, Enumeration District 64, Sheet 15B
17 Durham Street
Dwelling 216, Family 217
Kopp, Margaret, head, owns free of mortgage, female, white, 35, single, can read and write, born in Maryland, both parents born in Germany and spoke German, speaks English, no occupation
Kopp, Katherine, daughter, female, white, 16, single, not in school, can read and write, born in Maryland, both parents born in Maryland, speaks English, filer for telegraph company, wage worker
Kopp, Milton, son, male, white, 5, single, not in school, can read and write, born in Maryland, both parents born in Maryland, no occupation
Rumbel, George, father, male, white, 73, widowed, year of immigration 1870, naturalized in 1876, born in Germany, native language German, both parents born in Germany and spoke German, speaks English, watchman for packing house, wage worker
Rumbel, Frank, brother, male, white, 29, single, can read and write, born in Maryland, both parents born in Germany and spoke German, speaks English, driver of paint wagon, wage worker

1930 U.S. Census, Baltimore City, Maryland
6th Ward, Tract 10, Block 95, Enumeration District 4-70, Supervisor’s District 4, Sheet 1A
133 Bradford Street
Dwelling 3, Household 3
Cohen, Harry, head, owner, $2,000 in real estate, owns radio set, not on farm, male, white, age 27, married, not in school, can read and write, born in Russia, both parents born in Russia, native language Yiddish, immigrated in 1906, not naturalized, speaks English, occupation clerical worker for postal telegraph, wage worker, at work previous day
Cohen, Catherine, wife, female, white, age 24, married, not in school, can read and write, born in Maryland, both parents born in Maryland, no occupation
Cohen, Carroll R., son, male, white, age 3-6/12, single, not in school, born in Maryland, father born in Russia, mother born in Maryland, no occupation
Cohen, Irene M., daughter, female, white, age 6/12, single, not in school, born in Maryland, father born in Russia, mother born in Maryland, no occupation
Household 4
Kopp, Margaret, mother, female, white, age 45, unclear mark as to marital status, not in school, can read and write, born in Maryland, both parents born in Germany, speaks English, no occupation
Kopp, Milton C., brother, male, white, age 15, single, in school, can read and write, born in Maryland, both parents born in Maryland, speaks English, occupation messenger for postal telegraph, wage worker, at work previous day
Kopp, LeRoy E., brother, male, white, age 5, single, not in school, born in Maryland, both parents born in Maryland, no occupation

1936 Baltimore City Directory, page 717:
Kopp Milton C (Helen) office boy Balto Assn of Commerce h1911 n Castle

1940 U.S. Census, Baltimore City, Maryland
8th Ward, Enumeration District 4-167, Sheet 1A
1526 Chapel Street, household, rents, $18
Kopp, Milton C., head, male, white, 25, married, not in school, highest level of education 8th grade, born in Maryland, living in same place in 1935, not on a farm, at work week of March 24–30, 42 hours worked that week, machinist for air plane factory, wage worker, 26 weeks worked in 1939, income $546 in 1939, no other income
Kopp, Helen E., wife, female, white, 26, married, not in school, highest level of education 8th grade, born in Maryland, living in same place in 1935, not on a farm, not at work, not seeking work, engaged in housework, no other income
Kopp, Helen D., daughter, female, white, 7, single, in school, highest level of education completed 1st grade, born in Maryland, living in same place in 1935, not on a farm, not at work
Kopp, Gladys A., daughter, female, white, 6, single, in school, highest level of education completed “0”, born in Maryland, living in same place in 1935, not on a farm, not at work
Kopp, Ronald M., son, male, white, 2, single

Milton Kopp, Social Security Number 215-03-9724 issued in Maryland, was born 10 October 1914 and died in January 1976. His last record was from Zip code 21224 in Baltimore, Maryland

A death notice stated:
KOPP
On January 19, 1976, MILTON C., beloved husband of Helen E. Kopp (nee Hertel), father of Mrs. Helen Wilner, Miss Gladys A. Kopp, Messrs. Ronald M. and Melvin J. Kopp, and brother of Mrs. Katherine Cohen. He is also survived by 10 grandchildren and two great-grandchildren.
The family will receive friends on Wednesday and Thursday, from 2 to 5 and 7 to 9 P. M., at the funeral home of John A. Moran, Inc., 3000 East Baltimore street (corner of Potomac street), where funeral services will be held on Friday at 1 P. M. Interment in Parkwood Cemetery. [The Sun (Baltimore), 21 Janaury 1976, page C9; 22 January 1976, page C10; 23 January 1976, page C10.]