Brian Dennehy was nearly 40 when he first broke into Hollywood, but this didn't stop him from putting together a career that spanned over 60 films and 100 TV productions and stage plays. After completing his education, Dennehy started working as a stockbroker for Merrill Lynch in Manhattan during the mid-1970s. But by 1977, he'd decided that he wanted a life in show business, and soon became a fixture on the small screen with appearances on a number of popular TV series, including "Kojak," "M*A*S*H," and "Lou Grant." In 1981, he had a recurring role on the nighttime soap opera "Dynasty," and he later appeared on "Miami Vice," "Just Shoot Me!," and "30 Rock." But his breakthrough film role came in 1982, when Dennehy played the overzealous sheriff Will Teasle opposite Sylvester Stallone in "Rambo: First Blood." From there, he became known for his wide range of acting skills and was regarded as one of the best actors in the drama genre. During his career, Dennehy was nominated for Emmy Awards six times for his television movies. He won two Tony Awards, both times for Best Lead Actor in a Play. His first win was for "Death of a Salesman" (for which he also won a Laurence Olivier Award for the production's London run) in 1999, and the second was for Eugene O'Neill's "Long Day's Journey into Night" in 2003. According to Variety, Dennehy was "perhaps the foremost living interpreter" of playwright Eugene O'Neill's works on stage and screen.

After high school, Dennehy attended Columbia University on a scholarship for football. At 6'3", his size made him a natural on the football field, where he played offensive lineman for the Lions. By his sophomore year, he was starting on the team, was elected as a team captain, and became an All-Ivy League honoree. However, what he really wanted to do was join the campus acting group, The Columbia Players. But in those years, athletes were banned from joining campus performing groups. Struggling academically, Dennehy left Columbia after his junior year and joined the Marines, where he served in places like Japan and Korea. Following his military service he returned to Colombia, and after two more years of study, he graduated with the class of '65 with a Bachelor of Arts in history.

After embarking on his successful career as an actor, Dennehy remained a visible (and audible) supporter of his alma mater and its football program. In 2007, he was named Columbia's honoree at the bi-annual Ivy Football Association Dinner. In 2012, at the dedication of the Campbell Sports Center, he was a special guest in the ceremonial video honoring his former teammate. At Columbia’s request in 2016, Dennehy lent his distinct voice to a promotional video for the university. Colombia presented Dennehy with a John Jay Award for distinguished professional achievement in 1986, and in 2000 he was the college’s Class Day speaker.