According to the foreward of the publication for the Centenary Exhibition of Girl Guides "100 Years of Changing Lives", in 1909 a young group of women arrived uninvited at the first Boy Scout Rally in London at the Crystal Palace and demanded a place for girls. Robert Baden-Powell, the founder of Boy scouts, chose the name "Girl Guides" after a famous corps of guides in India. In 1910 his sister, Agnes Baden-Powell, became its leader. By 1912 Girl Guiding and Girl Scouting had spread to seventeen countries being actively engaged.
See Geni profile of Lord Baden-Powell's wife : Olave St. Clair Baden-Powell (St. Clair Soames) who continued the Girl Guides/Girl Scouts movement. Birth: February 22, 1889 Chesterfield, Derbyshire, UK Death: June 25, 1977 (88) Guildford, Surrey, UK. Place of Burial: Kenya
Some current UK organizations with archival material:
GIRL GUIDING UK http://www.girlguiding.org.uk
THE OLAVE BADEN-POWELL SOCIETY WAGGGS (World Association of Girl Guides and Girl Scouts) Olave Centre 12c Lyndhurst Road London NW3 5PQ
2012: GS USA's 100th anniversary and the 2012 Year of the Girl.
http://www.ob-ps.org/en/events/Events/philadelphia2012 The Olave Baden-Powell Society will be in Philadelphia, USA, May 17th - 20th, 2012"