History of Rangers

A Ranger or Ranger Guide is a member of a section of some Guiding organisations who is between the ages of 14 and 25. Exact age limits are slightly different in each organisation. It is the female-centred equivalent of the Rover Scouts

Early history

Girl Guiding had officially been founded in 1910 in the UK. By 1916-17, it had become apparent that girls who had been Girl Guides from the start were getting too old for their companies, and that older girls wished to become Guides but did not fit well in companies of younger girls. "Senior Guides" slowly came into existence as some captains (adult leaders of companies) formed patrols of girls over 16 years old. Robert Baden-Powell, the founder of Scouting and Guiding, was interested in this development and in June 1917 asked Rose Kerr to take on responsibility for them, outlining to her a plan for them. The scheme for the Senior Guides was published in parts in 1918.
In the next two years, many suggestions of name change were discussed but no consensus was reached. Rose Kerr recounts a conversation with Robert Baden-Powell in 1920 where he suggested "Ranger", one of the rejected suggestions for the Senior Scouts (by then called Rovers). In June 1920, Olave Baden-Powell, then the Chief Guide, wrote:

Here is the suggested new name: 'Ranger'. If you look it up in the dictionary, you will find it means quite a number of things. 'To range' is 'to set in proper order'; 'to roam', and this might well mean you are going to tread ground as a Senior Guide that as a Guide you have not yet passed.
'Distance of vision, and extent of discourse or roaming power' again shows that as a senior member of the community you are expected to look farther afield for good, and the work that you can do for the community.
'To range' means to travel, or to rove over wide distances, whether in your mind or your body. A Ranger is ' one who guards a large tract of land or forest,' thus it come to mean one who has the wide outlook, and a sense of responsible protective duties, appropriate to a Senior Guide. Another definition is 'to sail along in a parallel direction,' and so we can feel that the Ranger Guides are complementary to the Rover Scouts.
And so we hope that this new title will have the approval of all.

The name received approval at a Conference on County Commissioners in July 1920, and was thereafter the official name.

Girlguiding UK

In Girlguiding UK, Rangers is just one of the several branches of the Senior Section. Rangers belong to Ranger Units, open to girls from 14 to 26 years old. They can pursue any or all of several schemes, such as Look Wider, The Queen's Guide and the Duke of Edinburgh's Award. In Girlguiding UK, the terms Ranger and Ranger Guide are both used.
The Ranger promise is the same as that of the Guides:

I promise that I will do my best:

To do my duty to God,

To serve the Queen and my country,

To help other people

and

To keep the Guide Law.

But with the additional line that they are:
To be of service to the community.