First of, "Broadcast Hill" is the area off Barnett Street in east Fort Worth overlooking I-30 that is home to KXAS-TV's studios and a small tower complex that includes what was the original tower supporting the antenna of WBAP-TV when it signed on in 1948. That tower also originally supported WBAP-FM (now KSCS). WBAP 820 and WBAP-FM (KSCS) maintained their studios in a building at the base of that tower until 1993 when they moved to Lamar Blvd. in Arlington.
The area you refer to is generally called to as the Cedar Hill Antenna Farm. It now is home to 11 tall broadcast towers. The first was built in 1955 as a consortium between WFAA-TV and KRLD-TV (now KDFW). They formed the Hill Tower Corporation to cooperatively build one of the first "candelabra" towers in the nation, therefore ensuring that neither station had a height advantage. The Cedar Hill location was chosen because it is the highest point in the north Texas area, providing stations clear reach of both Dallas and Fort Worth (it became apparent in the 1950s that the two cities would be one single television market, so a station's tower would have to be centrally located to ensure full coverage.)
As TV was booming through the 1950s, the FCC and FAA helped ensure that the sites of these tall towers were not spread throughout a metropolitan area, but were instead concentrated in one area so as to be less of a navigational hazard to aircraft. WBAP-TV moved to the 3rd unoccupied arm of the Hill Tower from Broadcast Hill in the 1960s when NBC threatened to pull its affiliation if the network was not on equal footing against the CBS and ABC affillates in the market (the Cedar Hill location covered the entire DFW market much more effictively than WBAP-TV's east Fort Worth tower.)
Cedar Hill did not start to become the "tower farm" that it is now until the 1960s, when additional TV and FM operations necessitated new towers. Channel 11 moved from its own east Fort Worth tower onto a new tower shared with Channel 13. Doubleday built a tall tower for its new Ch.39, and another candelabra for UHF operations went up in the 70s for Channels 21, 27 and 33.
The original Hill Tower of WFAA/KDFW was struck by a Naval training jet in 1987, and left precariously imbalanced. The top 300+ feet of the tower was eventually removed and a "New Hill Tower" was built for WFAA and KDFW. At this time, Channel 5 opted out of the New Hill Tower, and constructed its own new tower.
The newest towers included a DTV candelbra (the southernmost tower and only one in Ellis, not Dallas, County) and the new CBS Radio tower which is only 3 years old.
Here's a quick summary of who is on what tower... (at least for the time being)
1. NEW HILL TOWER 1578ft. 3-arm candelabra KDFW Ch.4, WFAA Ch.8 and their DTVs.
2. OLD HILL TOWER 1240ft. Carries 5 backup FMs
3. SUSQUEHANNA TOWER 1558ft. Originally built for Ch.39, now carries 3 FMs: KPLX-99.5 at the top, and KDGE-102.1 and KDMX-102.9 further down on the side.
4. THOMAS TOWER 1029ft. Shortest major tower in the 'farm'. Carries 2 non-comm FMs: KNON-89.3 and KVTT-91.7
5. MILTON TOWER 1532ft. 3 TVs on its short candelbra: KTXA-21, KDTX-58 and KDTN-2; and one 3-FM panel: KLNO-94.1, KCBI-90.9 and WRR-101.1
6. COWBOY TOWER 1646ft. Another short candelbra with 3 TVs: KFWD-52 and its DTV and KPXD-68; along with the market's major shared FM antenna that carries 7 signals: KZPS-92.5, KLTY-94.9, KEGL-97.1, KLUV-98.7, KVIL-103.7, KKDA-104.5 and KHKS-106.1
7. KXTX TOWER 1535ft. Ch.39 and the DTV for KXAS
8. KXAS TOWER 1536ft. KXAS-5 and 2 FMs: KSCS-96.3 and KBFB-97.9
9. CBS RADIO TOWER 1731ft. The newest and tallest tower carries 3 of CBS' FMs: KJKK-100.3, KLLI-105.3 and KMVK-107.5
10. CBS TV TOWER 1587ft. KTVT-11 and KERA-13 and their DTVs along with KERA-FM 90.1
11. RICHLAND TOWER 1635ft. This candelbra is the southernmost tower and is now all-TV: KDFI-27, KDAF-33, KSTR-49 and their DTVs, along with numerous auxiliary facilities.
The above list is far from comprehensive, as there are also numerous LPTVs on the Cedar Hill towers, and I'm sure there have been some other facility changes that I can't recall off the top of my head, but that should give you a decent overview of things.
For more info and some great pics, you can also check out this great site:
http://www.fybush.com/site-021031.html (it's actually the first page of a four-part series on DFW tower sites!)