According to the New York State census of 1905, Gustav Kantz was living in the household of one Nicholas Schwanermann in Assembly District 14, Election District 22 (source: Reel 14 FHL microfilm 1433090). This A.D. and E.D. delimited East 13th Street, East 14th Street, Avenue B and Avenue C in the Lower East Side, now the East Village.

Gustav first married Louise F. C. Kahl (1882 – 8 March 1909) on 1 July 1906 (marriage certificate number 16317), at the St. George's Episcopal Church parish house, 207 East 16th Street New York, New York 10003-3746. Her burial location is Lutheran All Faiths Cemetery aka Lutheran Cemetery, 67-29 Metropolitan Avenue, Middle Village, Queens, New York 11379-1620 USA, Lot 1244 Map 3A.

They had two children:

William Kantz (28 March 1907 died at five hours old, birth certificate number 16400, death certificate 10949), burial location Lutheran All Faiths Cemetery aka Lutheran Cemetery, 67-29 Metropolitan Avenue, Middle Village, Queens, New York 11379-1620 USA, Lot 1244, Map 3A,

And

Margaret Anna Green née Kantz (New York, New York 14 July 1908 – Los Angeles, California 27 June 1959, burial location Hillside Memorial Park, 6001 West Centinela Avenue, Culver City (or Los Angeles), California 90045, Valley of Remembrance 16-882-3) whose spouse was Fischel Grunbaum aka Fischel Grünbaum mūtātō nōmine Philip Edward Green aka Philip E. Green aka Philip Green aka Phil Green (Lodzkie, Poland 15 December 1906 - 4 October 1962, burial place Hillside Memorial Park, 6001 West Centinela Avenue, Culver City (or Los Angeles), California 90045, Valley of Remembrance 16-882-4). She converted to Judaism.

Margaret Anna and Philip Edward had two children:

Louis Robert Green (New York 30 October 1928 – North Carolina 11 August 1983). Louis Robert is buried in New Bern National Cemetery, 1711 National Avenue, New Bern, Craven County, North Carolina 28560, Plot 8, 0, 6233.

and

Lorraine Green (?-?), nothing known.

In 1910, Gustav's address was on the Lower East Side, in Manhattan Ward 11 (bounded by Rivington Street on the south, East 14th Street on the north, Avenue B on the west, and by the Harlem River on the east).

Then he married Mary M. Kantz née Buckley "Nana" (city and county unknown, United Kingdom of Great Britain and Ireland 22 March 1888 – St. Elizabeth's Hospital (built 1926, went co-op in 1981), 689 Fort Washington Avenue, New York, New York 10040 February 1968) on 7 April 1912 (marriage certificate number 10210) at Church of the Annunciation, 88 Convent Avenue, New York, New York 10027-7520.

His address at the time was 606 East 14th Street, New York, New York 10009-3311, Lower East Side (torn down). Her address at that time was 1332 3rd Avenue, New York, New York 10075-1902 on the Upper East Side. She worked in a candy store owned by her parents.

When he registered for WW1 draft on 12 September 1918, he was a letter carrier working at 2414 Amsterdam Avenue, New York, New York 10033 with residence at 509 West 179th Street, New York, New York 10033-5708, Assembly District 23, Enumeration District (E.D.) and Tract unknown. The building was only a few weeks old.

Gustav and Mary were both buried in Gate of Heaven Cemetery, 10 West Stevens Avenue, Hawthorne CDP, Mount Pleasant, Westchester County, New York 10532-2205, Section 44, Lot 511, Grave 15.

[NOTE: In 1968 it was disclosed that a possible unidentified infant was buried with Gustav. It's highly unlikely they waited four years to have children and a stillborn or other infant death is highly possible. If it had been a girl, she would have been named Mary after the mother as was the custom. On the other hand, the infant could be Marie Gerardette Kantz erroneously Mary Kantz who was born and died in 1964.]

Gustav and Mary had three children:

Florence M. Leonard née Kantz (New York, New York 3 April 1916 - May 1972) married John J. Leonard Sr. (? - ?) on 29 August 1937 (marriage certificate number 19754) three children: Florence Brennan née Leonard (1949 -), John J. Leonard Jr. (1941 -2015), Philip T. Leonard (New York 2 August 1945 – Los Angeles, California 28 September 1970), in all cases burial locations unknown.

Grace Lillian O'Connor née Kantz (New York, New York 1918 – North Washington Avenue, Bergenfield, New Jersey ?) married William O'Connor (? - ?, burial place Las Vegas, Nevada)

[NOTE: Her name is shown as Grace D. Kantz on the 1940 Census.]

And

Matthew Henderson (no further information); no children in either marriage.

Philip Frank Kantz (Harlem Hospital (construction began 1887, now called Harlem Hospital Center), 506 Lenox Avenue, New York, New York 10037 14 July 1922 – Morrisania Hospital (built 1929, closed 1976), 50 East 168th Street, Bronx, New York 10452-7929 4 October 1968)

married

Marcella Marie Kantz née Shine (New York, New York 5 April 1921 – St. Louis, Missouri 23 December 2004). They are buried in Long Island National Cemetery, 2040 Wellwood Avenue, Farmingdale, Suffolk County, New York 11735-1213, Section 2P, Site 1085.

Gus Kantz was a mailman for the US Post Office Department; he retired c. 1960. He worked most of his career at the post office located 2414 Amsterdam Avenue, New York, New York 10033 between 179th and 180th Streets in the Washington Heights section of New York City. The building still stands as of early 2018.

Gus' and Mary's last address was a first-floor one-bedroom apartment on Nagle Avenue, New York, New York 10040.

ANECDOTES:

---Gustav was author of the cheerful canard that the deed to the city of Worms-am-Rhein was hidden in the Ernst-Ludwig-Brücke. The deed said that ownership of Worms-am-Rhein would pass to a Kantz named Philip. Alas, the Ernst-Ludwig-Brücke was destroyed by the retreating Wehrmacht Heer 20 March 1945 and replaced 1951-1953 by the Nibelungenbrücke Worms.

---Gustav had an unidentified relative, probably a cousin, who disappeared in Panamá while working on the Canal during the American construction period, 1904-1914. He "put ads in all the papers", according to son Philip, but to no avail.

---Gustav was fond of Kümmel, "a sweet, colorless liqueur flavored with caraway seed, cumin, and fennel" of Dutch origin; he probably acquired the taste from Hessian cookery's use of caraway.

---Gustav fancied himself a poet; two examples: "Herman the German has lost his Messerschmidt" and "Where was Moses when the lights went out? Down in the cellar eating sauerkraut."

---Gustav was an irrepressible wit: whenever a Western Union messenger delivered a telegram to his apartment, Gus would shout, "Give him an onion!"

---Gustav was an avid stamp collector. While delivering mail, if he saw an interesting stamp, he would hand-deliver the letter and ask the addressee for the stamp in exchange for his efforts.