At age 8 he and his family moved to Illinois. At age 19 he moved to Iowa to start his business career. He later co-founded Iowa Savings Bank in Coon Rapids.
Garst and Elizabeth Johnson had one child, Ada Belle Garst.
He was later married to Clara H. Clark and had two children: Louise Garst and Warren Carroll Garst Junior.
He served in the 25th through 31st General Assemblies. He was nominated for lieutenant governor at the Republican Convention in 1906 and was inaugurated on January 17, 1907.
When Governor Albert B. Cummins was elected into the United States Senate he was elevated to the position of Governor of Iowa. During his short time as governor he carried out the Cummins administration"s policies.
When his term ended he was urged to run for a full term as governor.
He lost to State Auditor Beryl F. Carroll by 25,000 votes. He died on October 5, 1924 and was buried at the Glendale Cemetery in Des Moines, Iowa.
Member Iowa Senate, 25th to 31st General Assemblies (chairman appropriation committee for 5 sessions).
Married Clara H. Clark, November 27, 1889.