The Arch/sign was placed farther west on Katella when DCA first opened, so late 2000. It was a gate for the Convention Center visitors and/or DLR guests parking at the Convention Center. That is why the traffic Light was placed near the Convention Center Arena, aka the first Anaheim Arena. Currently the term Anaheim Arena is the legal name for the Honda Center, since the sponsor could change.
As part of the Cars Land expansion, it was moved to the current location.
The main reason for the gate was for a tram stop. When DCA first opened, Disney got a Waiver to allow the trams to cross Disneyland Dr. to service Simba with a stop behind the PPH. So, they could stop at the Convention Center gate when needed, such as during NAMM.
The last time I used the gate when I parked at Angel Stadium for an ACC event. ART used public buses (Toy Story Buses) to drop us off at the gate, entering the Disney Way driveway, and headed south to the gate. So you walked a few feet to the gate, and crossed at the light. That was a couple of yeas ago. I believe ACC North was still under construction.