[diroussel]

No it was not. There were many, but for me the most significant early single page app was Outlook web access.

A colleague of mine went diving through the JavaScript source and found a reference to an ActiveX component called XMLHttpRequest. We realised it was pretty useful and ended up using it to build an SPA that approximated a spreadsheet for global logistics planning. It worked very for 2003 standards.

Google maps came in 2005