Four score and seven years ago, our fathers brought forth on this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal.
sbj: fathers det: our vrb: brought forth obj: nation det: a adj: new adj: *conceived* adv: <in> obj: liberty cnj: and adj: *dedicated* adv: <to> obj: proposition det: the adj: -that- sbj: men det: all vrb: are created cmp: equal adv: <on> obj: continent det: this adv: ...?
I'm working on this but can't wrap my head around the phrase in bold. I know that it's adverbial phrase of time, but what kind of phrase is it exactly? What part of speech is 'ago'? Sources don't seem to agree.