British albums in the 60's typically had 14 tracks--7 per side. The American counterpart had only 12, so some of the tracks "lost" in America would be included on later compilations.

To the best of my knowledge, the first American release of a British group to contain all 14 songs was "Face to Face" by the Kinks.

I don't know this from research or evidence, but my belief has always been that either the band or their American label (Reprise) believed that the work was so unified / consistent that all 14 tracks would have to be included.

Regardless of the aesthetics / marketing of the release, "Face to Face" is the first rock album in my experience to provide an emotionally / thematically unified experience. Some consider it the first concept album, but that depends on how you define "concept album." What's true of the work in any case is that each track informs all the others, and the sequencing of tracks is essential--far before Sergeant Pepper.