(Edit: see below, Neverwinter Nights by AOL was the First MMORPG but no longer in service, The Realm Online is next and is still in service.)
Asheron's Call was released November 2nd, 1999 and was/is developed by
Turbine, Inc. and published by Microsoft which, at the time of release, used MSN Zone to log into the world and register for the game. In 2004 Turbine did away with MSN Zone when they purchased the rights (a year earlier in 2003) to the franchise from Microsoft and allowed users to migrate their old MSN Zone characters to the Turbine database, which I did for 2 of my AC accounts. Was sweet to pick AC back up after not playing it for nearly 7 years, import my OLD arse characters, and play.
More information on older MMORPGs:
Neverwinter Nights (AOL), released March 1991. (Oldest MMORPG but is no longer in service, ended in 1997)
The Realm Online, released March 1995. (Oldest MMORPG still in service)
The rest are all also still in service and worthy of being mentioned as paving the way for the spectacular MMORPGs we see today:
Meridian59, released December 15th 1995 in a early stage then fully published/released in September 1996.
Furcadia, released December 16th 1996.
Ultima Online, released September 25th 1997.
Everquest, released March 16th 1999.
Asheron's Call, released November 2nd 1999.
Just to note, MUDs (text based roleplaying online games), have all MMORPGs beat of course. I do not think the OP was referring to MUDs however since he refers to Ultima Online, an MMORPG.