Shortly after this hit, the older three left high school to start touring, the youngest of the four, Mary Weiss, stayed behind to finish school. The combination of three out of the four members performing together at one time continued throughout the band's career, though the missing member was not always the same. This created a bit of a mystique around the band, which has never quite been solved because the surviving members rarely talk to the press.
The quality of Morton's work with The Shangri-Las on Red Bird was remarkable considering that he had virtually no prior experience in the music business. The group's material, so over-the-top emotionally that it sometimes bordered on camp, was lightened by the first-class production, which embroidered the tracks with punchy brass, weeping strings, and plenty of imaginative sound effects. Nowhere was this more apparent than on "Leader of the Pack", with its periodic motorcycle roars and crescendo of crashing glass. The death-rock classic became the Shangri-Las' signature tune, reaching #1 on November 28th, 1964. To record "Leader Of The Pack", a motorcycle was brought into the hall just outside the recording studio and the sound of its revving engine was incorporated into the mix, along with that of a bike crash toward the end of the song. The hit topped the charts and helped to establish the Shangri-Las' image as tough, street wise girls who might be part cheerleader, part biker's moll. It fit the mould of teenage disaster songs that were popular in the early '60s and was spoofed by a group known as the Detergents with "Leader Of The Laundromat", which was itself a top twenty tune. "Leader Of The Pack" was also very popular in the UK, charting four separate times from 1965 to 1976, although it was the Shangri-Las' final hit on the UK charts.
The girls were hot. They came to epitomize the Brill Building sound and had a wide appeal with the young record-buying public. They continued to turn out hits on the Red Bird label. "Give Him A Great Big Kiss" (#18 in 1965) had the sound of a big smooching noise. "Out In The Streets" (#53 in 1965), "Give Us Your Blessing" (#29 in 1965) and "Right Now, Not Later" (#99 in 1965) were followed by "I Can Never Go Home Anymore" (#6 in 1965), their final US Top Ten entry, and "Long Live Our Love" (#33 in 1966), their last tune to reach the American Top 40. An attempt to cover Jay And The Americans' hit, "She Cried" with their own "He Cried" stalled at #84 in April, 1966. Another curious song that the Shangri-Las recorded before leaving the charts for good was "Past, Present and Future", (#59) which the Who's Pete Townshend has listed as one of his all-time favorite recordings.
Red Bird went out of business in 1966 and The Shangri-Las did some work for Mercury, but could never duplicate their earlier success. There are other recordings in existence that some attribute to the Weiss and Ganser sisters, but it is unclear who really did them. This list would include "Wishing Well" by The Shangri-Las on Spokane, "Only Seventeen" by The Beatlettes on Jubilee, and "What's Wrong With Ringo?" by The Bon Bons.
Unlike some girl groups, The Shangri-Las were dynamic on stage performers, choreographing their dance steps to their lyrics, and wearing skin-tight leather pants and boots that were quite daring for the time. Their real lives however, were not without elements of drama themselves. Their constant personnel changes baffle historians; sometimes they are pictured as a trio, and sometimes one of the members in the photos is clearly not one of the Weiss or Ganser sisters. Even today, The Shangri-Las' history remains somewhat murky. The remaining members rarely reunited for oldies shows or talked to the press. The Shangri-Las that appeared in public performances in the late 1990s did not contain any of the original members.
George Morton went on to produce Janis Ian, Vanilla Fudge, Mott The Hoople, The New York Dolls, and others. There were rumors of a Shangri-Las reunion in the '70s, but Mary Ann Ganser contracted encephalitis and died in 1971, and her sister Marge battled breast cancer and passed away in 1996.
In March, 2007, Norton Records released a critically acclaimed solo album by Mary Weiss called "Dangerous Game". She continued performing in the United States, Spain and France and was said to be working on a new album for 2010. As of early 2012, that album had still not appeared. Her website did not list any personal appearances in 2017 for the now 68-year-old singer.
The Shangri-Las vocal style and physical appearance, along with the energy and flair of their producer, George Morton, combined to make them one of the great girl groups of the 1960s.