My recollection was that Outlook's Web Access was the first. IIRC, it used what would become XMLHttpRequest when it was still internal to Microsoft, so it's the first of what we might consider to be modern web application. GP's 1997 seems right on, though, since that was the first release.

https://en.wikipedia.org/wiki/Outlook_on_the_web#History_2

Microsoft invented AJAX specifically for Outlook Web Access so yes that is in fact the first "modern" web application.

As I recall there was a fight about getting it in and the creators called it XMLHttpRequest because XML was the hotness at the time and that got it past the project managers and PHBs.

GP cites Squirrelmail, which definitely was not AJAXy. And still isn't, I'm pretty sure.

What I mean was:

-Webmail was already established as a "thing" when Gmail came out, even in Universities.

-Gmail wasn't particularly special from a UI perspective and was comparable to other offerings at the time.

-There was plenty of other web apps already that weren't Google products. In fact, I, personally, was writing one at the time GMail came in out.

Sure webmail had been out for a decade before GMail. But I believe the point was that Gmail was special in that it was a pioneering user of AJAX-style interactivity.

Pre-AJAX, web-based services were just a series of forms, and the interactivity patterns harkened back to "smart terminal" [1] form-based use for mainframes in the 1970s. I believe the user you were responding to uses "application" to mean something approximating the desktop application experience of the 80s or the current mobile app experience.

So the distinction they're drawing is about the kind of interactivity. Squirrelmail, et al, were a series of forms and pages. GMail didn't do a new page or frame load every time you looked at a new message. UI rendering and interactivity became client-only activities, with the server providing an API.

[1] now known as block-oriented terminal: https://en.wikipedia.org/wiki/Block-oriented_terminal