William Haislip Squier was born on May 12, 1950, in Boston, Massachusetts. Growing up, he was influenced by Eric Clapton's music and learned to play the guitar. After completing high school, Squier attended Berklee College of Music and established his first band, Kicks, in the early 1970s. He later joined the band Piper, which gained moderate success, including opening for KISS during their late 1970s tours.

Squier's solo career began in 1980 when he signed his first deal and released his debut album, The Tale of the Tape. The album spent three months on the Billboard charts and spawned a few moderately successful singles. However, it was his 1981 album Don't Say No that brought him significant breakthrough success, reaching the top twenty on the mainstream charts and spawning the singles "My Kinda Lover" and "In the Dark."

Throughout the 1980s, Squier released several successful albums, including Emotions in Motion (1982), Signs of Life (1984), Enough is Enough (1986), and Hear & Now (1989). Some of his notable hits during this period include "Everybody Wants You," "Emotions in Motion," "Rock Me Tonite," and "Love is the Hero." Squier's music was widely played on rock radio and MTV, establishing him as a prominent figure in arena rock.

In the 1990s, Squier released three more albums: Creatures of Habit, Tell the Truth, and Happy Blue. Although these albums did not achieve the same level of success as his 1980s releases, Squier continued to maintain a presence in the music industry. His songs have been featured in various films and video games, and his music has been sampled by numerous artists, including Eminem, who sampled "The Stroke" in his 2013 hit "Berzerk."

Squier's music has had a lasting impact on the industry, with his song "The Big Beat" containing one of the most-sampled drum breaks, used by artists such as Run-DMC, Alicia Keys, and Jay-Z. His influence can still be heard in contemporary music, and his legacy as a pioneering figure in arena rock continues to be celebrated.

Despite largely stopping his recording career after the commercial failure of Tell the Truth in 1993, Squier has continued to perform live, including smaller tours and one-off concerts. He has also collaborated with other artists on occasion, contributing to various projects and charitable causes, such as an album to benefit the victims of Hurricane Sandy.