Sources

Data from https://books.google.com/books?id=PbMdeizaCNcC&pg=PA402

U.S., Departing Passenger and Crew Lists, 1914-1966

Name: David R Sparks
Birth: abt 1898
Departure: 4 May 1921 - San Juan, Puerto Rico, USA
Occupation: novelist

1930 census

shows him living in Whitefield, New Hampshire, recorded as a writer for a magazine. Born Illinois.

US passport

Name: David Rhodes Sparks
Age: 22
Birth Date: 3 Nov 1897
Birth Place: Alton, Illinois
Residence Place: Alton, Illinois
Passport Issue Date: 18 Sep 1920
Father: Charles F Sparks
Has Photo: Yes
Certificate Number: 91932