The album was the band's first release for A&M Records(whom they signed to earlier in 1975 after the unexpected success of the single "Lady").
The album also marked the final appearance of original Styx guitarist John Curulewski who left abruptly following the release of Equinox. The band went into a frantic search to find a replacement for their upcoming tour to support Equinox. Soon after, they found Tommy Shaw.
The album's biggest hit was the track "Lorelei" which was Styx's second US Top 30 hit. Another well known song in the album was "Suite Madame Blue" which was written about the upcoming Bicentennial of the US and the track would be a staple for all Styx tours with Dennis DeYoung save the 1981/82 Paradise Theater tour.
Although Equinox stalled at #58, it would go Gold in 1977 shortly before the release of The Grand Illusion.