Glen Highlands is an area in Montclair that used to be at least four or five separate areas, that have been combined into one, I assume by the Real Estate Agents of today. The areas were Glenwood, Glenwood Extension, Glenwood Park, Glenwood Pines, Fernwood and maybe some of Merriewood. Each were sold a "unique" and different subdivisions by Real Estate Companies.
Glenwood Park went on sale November 1920, it was sold by Vila Site Sales part of the Realty Syndicate.
I'm not from this immediate area, but in my mind Glen Highlands is the entire area between 13, 24, and the Thornhill area. I've never even heard of "Merriewood" before seeing it on Greenstreets-sourced maps. On another note, everyone I know refers to this area as "Broadway Terrace" after the main road running through it and the exit on 13. Someone who's native to this neighborhood may be able to provide better insight. -Charlie