Dallas has long been called “Big D.” In the 1990s, “H-Town” became a hip-hop nickname for Houston, and “D-Town” soon followed.

“D-Town” was used in CB-radio slang in the 1970s for Dallas. (Denver and Detroit also lay claims on “D-Town.") The Dallas nickname was not widely used in the 1980s. When “D-Town” entered hip-hop in the 1990s, it was independent of the CB use of the same nickname.


Urban Dictionary
d-town
dallas texas, where da hustlas and headbussas are formed
D-town representin dat dallas texas, not no detroit or denver
by Rick D May 15, 2004

d-town
Dallas, Texas
-Not Detroit-
-Not Denver-
That’s were we represent Big D and youn know it remember don’t mess with Texas the bigeer state than colorado and michigan. D-Town been labeled here first in Dallas. Forget detroit rock city and denver
by C-Thuggie Dallas, Texas Sep 9, 2005

D-Town Records
D-Town Records/Eig Group Dallas, Texas’ new R&B/Hip Hop label, is one of the fastes growing independent record labels in the country and is determined to bring a fresh new image and sound to the music industry. The stars at night are definitely huge and immaculately brighter thanks to its emergence.
CONTACT US AT
EIEG Group/DTR/Koast2Koast
1015 N. Interstate 35E
SUITE 204
Carrollton, TEXAS 75006

Google Books
Cassell’s Dictionary of Slang
by Jonathon Green
Sterling Publishing Company, Inc.
2006
Pg. 456:
D-town n. [1970s] (US) Dallas. Texas.

6 March 1976, Dallas (TX) Morning News, section D, pg. 3:
“Howdy, Big Mack rig. How does it look over your shoulder toward Big D town?”

7 June 1991, Fort Worth (TX) Star-Telegram, pg. 12:
The largest event in the history of downtown D Town is not the orgy that is Texas-OU weekend, or anything associated with the Cotton Bowl.

Google Groups: rec.music.misc
Newsgroups: rec.music.misc, alt.rap
Followup-To: rec.music.misc
From: (NORTH, TOM-C)
Date: 23 Apr 92 17:25:00 GMT
Subject: Re: Rap is an art. (was Re: THE TEN MOST OVERRATED ROCK BANDS EVER)

I just want to add to this. I am a white guy from Texas, I like all types of music, but take a special interest in rap. I am from D-Town (Dallas), but what is sad is that some people is know (primarily white) are always talking SHIT about rap. 

Google Groups: rec.music.makers.builders
Newsgroups: rec.music.makers.builders
From: (Jeffrey L. Suits)
Date: 1996/03/21
Subject: Re: Dallas Guitar Show

Gregg Hopkins will be manning the booth in D-town.