Historically, the order welcomed girls from age eleven to twenty years old with or without a family connection Freemasonry.

The first Initiation consisted of a class of 171 young women on April 6, 1922, in the auditorium of the Scottish Rite Temple in McAlester, Oklahoma.

The authority of the district deputy is limited to inspecting the ceremonial work of the assembly and providing guidance at the request of the advisory board or supreme inspector/deputy.

Generally, to be appointed or elected to a Grand Floor Office, a member must be a past or present worthy advisor in her assembly.

Recipients of the award (Masters of the Grand Cross of Color) are expected to meet once per year for a special service.

In addition, adult sponsors without Masonic affiliation are awarded the Service to Rainbow in place of the Grand Cross of Color.

The countries outside the United States that have assemblies are Aruba, Australia (in Queensland, New South Wales and South Australia), Bolivia, Brazil (in Parana, São Paulo, Distrito Federal, Minas Gerais, Mato Grosso do Sul, Tocantins, Pará, Espírito Santo and Santa Catarina [ Biguaçu ]), Canada (in Ontario and New Brunswick), Paraguay (in Asuncion, Encarnación, Ciudad del Este and Concepción), the Philippines, Italy, Mexico, and Romania.

Rainbow has had assemblies in other countries, mostly due to American military presence: Cuba, Germany, France, Panama and Vietnam.

The members of that Assembly will meet with the young woman to answer any questions she or her parents/guardians may have and to make sure she is a proper candidate to receive the degrees.

A proper candidate, by guidelines of the order is a girl within the appropriate age range who believes in the existence of a Supreme Being, does not cohabitate with a significant other, has had no children, is not pregnant, has never been married, and has the permission of her parents/guardians to become a member.

[15] For girls between ages 6 and 10, some jurisdictions have a "Pledge" program for prospective members, so that they can become familiar with Rainbow ceremonies and activities.

For this to be granted, the young woman must write a letter expressing her interest in extending her active service and present it to her Supreme Deputy/Inspector.