After leaving high school, the next stop for Hammerstrom was Union College in Schenectady where he made a name for himself. In 1936 he captained the freshman squad to an undefeated season. Hammerstrom proceeded to letter on the varsity for the next three years (1937-1939), with a sensational senior season. The "Big Swede," as he was known around the campus, captained the 1939 Dutchmen to a 7-0-1 record, which was the first of the school's six undefeated regular seasons.
Hammerstrom, who was also known to his football foes as "Slammin' Sammy," established a Union single-season rushing record with 1,143 yards. That total stood as the Union milestone for 50 years until Ryan Mason gained 1,545 yards in 14 contests in 1989 when the Dutchmen lost the NCAA Division 3 championship to Dayton University.
Hammerstrom put together seven 100-yard rushing performances with the school's all-time best effort bringing 236 yards on November 11, 1939, against the University of Rochester. The only team to keep him under 100 yards was arch-rival RPI.
When not carrying the football, the triple-threat Hammerstrom completed 21-of-35 passes and also did the place kicking and punting. He accumulated 86 points on 13 touchdowns and eight extra point kicks to make him the East's top scorer and fourth in the nation.
For his accomplishments, he was chosen to the Associated Press Small College All-American team, which was the first time that a Union player had ever received the honor. In addition, he was selected to the AP All-Upstate New York All-Star Team, which was comprised of players from both major and small colleges. Hammerstrom, who was then 6-foot-1, 183 pounds and was larger than two of the five linemen, was named to the All-American squad and played in two all-star games.
First, he was a member of the New York Herald Tribune's Eastern All-Stars, who played the New York Giants on September 4, 1940, at the Polo grounds in New York City. Then on September 10 at Boston's Fenway Park, he joined The New England All-Stars who met the Washington Redskins.
The total rushing figures of Hammerstrom's three-year varsity career aren't available because accurate records weren't kept back in the l930s.
Hammerstrom, thanks to his brilliant senior year, attracted the attention of the Giants, and then the Detroit Lions wanted his services. The Giants sent him a contract and a letter in January of 1940 that was signed by Secretary Wellington T. Mara to play an 11-game schedule at $150 per game. The Giants, who are still owned by the Mara family, would have paid 75 percent of the $150 after each game with the remaining 25 percent at the close of the season or upon release of the player.
Hammerstrom, who was later married in February of 1940, decided to take a teaching position at a yearly salary of $1,300. Later that year, Detroit Coach George "Potsy" Clark invited Hammerstrom for tryout, but he again declined.
While also at Union, Hammerstrom was the intramural heavyweight boxing champion in 1938 and played on the varsity basketball team for his final two years with a letter earned in 1940.
Hammerstrom was also involved in various student activities on the campus. He was a two year member of the student council, vice-president and later president of his class, a member of the Garnet Key College Hospitality and the Terrace Council Senior Honorary Society. He also joined the Lambda Chi Alpha Fraternity as a freshman, served as secretary as a sophomore, treasurer as a junior and president as a senior.
One of his top honors was earning the prestigious Bailey Cup given for his overall contributions at Union.
Just prior to coming back to Jamestown in 1947, he coached an undefeated 1946 football team at Massena High School, which still has two of the longest winning streaks in the state scholastic circles.
From 1947-1949, Hammerstrom headed up the Jamestown football program with a fine record of 15-9. Highlighting those years was the 8-0 1949 team, marking the school's first perfect season since being 8-0 in 1898. When he left Jamestown to return again to Union as the football coach, the Red Raiders were on a 10-game winning streak.
Hammerstrom coached the Dutchmen from 1950-1957 and recorded a 26-34-2 mark with his finest season being in 1956. That year Union was 6-2 and he was chosen Coach of the Year by the Northeastern New York Sportswriters.
Additionally, he was the freshmen basketball coach in 1950-1951 and the coach of the 1957 golf squad.
Although his record wasn't that outstanding, he was highly-respected for all his contributions as a physical education teacher and coach during his Union days. He left Union in 1957 and moved to Arizona because of his son's illness. However, before leaving he was given a farewell dinner by Union. Then college president Carter Davidson said, "Sam Hammerstrom has been the ideal football coach at Union because he has combined careful study of the game with a sincere devotion to the highest ideals of the college."
Hammerstrom was the head umpire for the Madison Little League in Phoenix, Arizona, in 1960-1961 and Eastern secretary for the American Football Coaches in 1956.
He was a member of the Jamestown American Legion from 1947-1950, the Schenectady Rotary Club 1956-1957 and treasurer of the Schenectady Girl Scouts Council in the 1950s. Also he was on the Wickenburg, Arizona, Town Council from 1966-1969 and the mayor in 1968-1969.
In Camp Verde, Arizona, he was with the Lions Club from 1970-1976 and with the Kiwanis Club from 1982 to the present time. Before retiring, Hammerstrom was the Camp Verde School District superintendent.
In 2003, Hammerstrom was inducted into the second class of Union College Athletic Hall of Fame.
Lawrence Lentchner said the following about Hammerstrom in the Union College 1959 weekly newspaper (Concordiensis) article. "Sam's teams were noted for their aggressiveness, good spirit and sportsmanship, just as he was. In short, the Sam Hammerstrom-Union College relationship was an excellent and close one - one that will be remembered many years from now."