I did their bio on Genius a while ago. The shorter version:
The Angels, originally The Starlets (Allbut Sisters + Bernadette Carroll + Linda Malzone), mostly sang backups for other groups. Linda Jankowski replaced Malzone, and Carroll went solo. That's when they became The Angels and released "Till". Then Jankowski went solo, replaced by Peggy Santiglia. That's when they hit #1 with "Boyfriend". They also kept singing backups for Neil Diamond, Lesley Gore, Tony Orlando, Jackie Wilson, Frank Sinatra, and Lou Christie. Santigilia went solo (under the name Peggy Sans) and was replaced by Toni Mason and they became The Halos. But after scoring no hits under that name, they re-formed The Angels with Debbie Swisher. But they still had no hits. However, they went on to be a nostalgia touring act when Santiglia rejoined the group in 1969.
The Angels, originally The Starlets (Allbut Sisters + Bernadette Carroll + Linda Malzone), mostly sang backups for other groups. Linda Jankowski replaced Malzone, and Carroll went solo. That's when they became The Angels and released "Till". Then Jankowski went solo, replaced by Peggy Santiglia. That's when they hit #1 with "Boyfriend". They also kept singing backups for Neil Diamond, Lesley Gore, Tony Orlando, Jackie Wilson, Frank Sinatra, and Lou Christie. Santigilia went solo (under the name Peggy Sans) and was replaced by Toni Mason and they became The Halos. But after scoring no hits under that name, they re-formed The Angels with Debbie Swisher. But they still had no hits. However, they went on to be a nostalgia touring act when Santiglia rejoined the group in 1969.