Q1: Why is this page not limited to members of the 75th Ranger Regiment?
A1: (1) There is already an article called 75th Ranger Regiment. Limiting this article to members of the 75th Ranger Regiment would create a duplicate article. (2) Reliable sources define the term 'Ranger' in different ways—which include graduates of Ranger School, as well as members of historical units besides the 75th Ranger Regiment. See the section in the article on 'the term Ranger' for more information.
Q2: Why isn't the name of the article 'United States Army Ranger'?
A2: There was an RFC regarding this topic (see talk page). There was support for the move, but it was not overwhelming.
