Seymor Lowman was born in Chemung, New York on October 7, 1868, the son of John Lowman (1832–1884) and Fanny (Bixby) Lowman. He was raised in Bainbridge, and completed his high school education at Bainbridge Union School. He then graduated from Lowell's Business College in Binghamton, and became a school teacher. He studied law with attorney John W. Church of Norwich, was admitted to the bar in 1891, and practiced in Elmira. On September 9, 1893, he married Katherine Harding Smith, whom he had known while growing up in Bainbridge.
Lowman became active in local politics as a supporter of the campaigns of Jacob Sloat Fassett. He was a member of the New York State Assembly (Chemung Co.) in 1909 and 1910, and also Chairman of the Chemung County Republican Committee from 1912 to 1934. He was a member of the New York State Senate (41st D.) from 1919 to 1924, sitting in the 142nd, 143rd, 144th, 145th, 146th and 147th New York State Legislatures, as well as a delegate to the 1924 and 1932 Republican National Conventions.
He was Lieutenant Governor of New York from 1925 to 1926, elected at the New York state election, 1924 on the Republican ticket. At the same time, Democratic Governor Al Smith was re-elected, while his running mate George R. Lunn was defeated. Lowman was the last lieutenant governor of New York who was not the running mate of the elected governor. At the New York state election, 1926, he was defeated for re-election when Al Smith was re-elected with his running mate Edwin Corning.
From August 1, 1927 until the end of the Hoover administration in 1933, Seymor Lowman was Assistant U.S. Secretary of the Treasury under Andrew W. Mellon and Ogden L. Mills, and as a well-known "dry" (against the sale and consumption of alcoholic beverages) was in charge of the enforcement of Prohibition. A month after taking office, he stated: "There are many incompetent and crooked men in the service. Bribery is rampant. There are many wolves in sheep's clothing. We are after them... Some days my arm gets tired signing orders of dismissal." 
After leaving office Lowman served as president of the Elmira Savings Bank.
Lowman died in Elmira on March 13, 1940. He was buried at Riverside Cemetery in Chemung.
- TIME Magazine on September 19, 1927 (giving middle initial "M.")
-  The tariff imbroglio with France, in TIME Magazine on October 17, 1927
-  TIME Magazine on July 25, 1927
|New York Assembly|
David C. Robinson
| New York State Assembly
Robert P. Bush
|New York State Senate|
Morris S. Halliday
| New York State Senate
James S. Truman
George R. Lunn
| Lieutenant Governor of New York