PRE-1970 STATIONS (NOT O & O) STILL WITH THEIR DEBUT NETWORK

[gregg75]

*****Ok to list those with secondary networks, since most either
dropped them or made little use of them*****

So many have switched, who remained true and never switched?

WCYB 5 Bristol NBC
WRBL 3 Columbus GA CBS
WTVM 9 Columbus GA ABC
WALB 10 Albany GA NBC

[KeithE4]

All three pre-'70 Tucson stations - KVOA 4 (NBC), KGUN 9 (ABC) and KOPO/KOLD 13 (CBS) are with their original networks.  As are KOAI/KNAZ 2 Flagstaff and KTYL/KVAR/KTAR/KPNX 12 Mesa/Phoenix (NBC).  The former is now a satellite of the latter, but as a standalone it was NBC.

Others I can think of are:
Detroit MI:  WWJ/WDIV 4 (NBC) and WXYZ 7 (ABC)
Washington DC:  WMAL 7 (ABC) and WOIC/WTOP/WUSA 9 (CBS)
Wausau/Rhinelander WI:  WSAU/WSAW 7 (CBS), WAOW 9 (ABC), WAEO/WJFW 12 (NBC)
Springfield MA:  WWLP 61/22 (NBC)
South Bend IN:  WNDU 46/16 (NBC, WSBT 34/22 (CBS)
Terre Haute IN:  WTWO 2 (NBC), WTHI 10 (CBS)
Cedar Rapids/Waterloo IA, WMT/KGAN 2 (CBS), KWWL 7 (NBC), KCRI/KCRG 9 (ABC)
Milwaukee WI:  WTMJ 3/4 (NBC)
Madison WI:  WISC 3 (CBS), WMTV 33/15 (NBC)

Some of those stations had secondary affiliations at one time, but their primary networks haven't changed over the years.

[bpatrick]

We have several in North Carolina:

WFMY Ch. 2 Greensboro (CBS, signed on 1949)
WBTV Ch. 3 Charlotte (CBS, 1949)
(the two oldest CBS affiliates south of Washington, DC)
WWAY Ch. 3 Wilmington (ABC, 1964)
WECT Ch. 6 Wilmington (NBC, 1954)
WITN Ch. 7 Washington (NBC, 1955)
WNCT Ch. 9 Greenville (CBS, 1953)
WCTI Ch. 12 New Bern (ABC, 1963)
WXII Ch. 12 Winston-Salem (NBC, 1953)
WLOS Ch. 13 Asheville (ABC, 1954)

In the I-85 corridor between Raleigh/Durham and
Atlanta, Greenville/Spartanburg/Asheville is the only
market where the ABC, CBS, and NBC stations are
with the same networks they started with; WYFF
Ch. 4 Greenville has been with NBC since 1953;
WSPA Ch. 7 Spartanburg has been with CBS since
1956.

And elsewhere in South Carolina:

WIS Ch. 10 Columbia (NBC, 1953)
WLTX Ch. 19 Columbia (started as WNOK Ch. 67
   in 1953 but has always been CBS primary)
WOLO Ch. 25 Columbia (ABC, 1961)
WCSC Ch. 5 Charleston (CBS, 1953)
WBTW Ch. 13 Florence (started on Ch. 8, but has
  been CBS primary since 1954)

Roanoke/Lynchburg is another where the ABC, CBS,
and NBC stations have maintained their primary affiliations:

WDBJ Ch. 7 Roanoke (CBS, 1955)
WSLS Ch. 10 Roanoke (NBC, 1952)
WSET Ch. 13 Lynchburg (ABC, 1953--the oldest ABC affiliate
  south of Washington; WLOS is second)

I frequently post retros from the Kentucky edition of TV Guide;
the three NBC affiliates: WAVE/3 Louisville (1948), WLWT/5 Cincinnati
(1948), and WLEX/18 Lexington (1955, I believe) have stayed with
their original primary network.

Also, WSMV Ch. 4 Nashville (NBC, 1950)
        WTVF Ch. 5 Nashville (CBS, 1954) (WSIX, now WKRN, was
the CBS primary affiliate for about a year before what was WLAC
signed on; WSIX then became ABC.)

[MattParker]

O&O status can change, too.
WXYZ-TV was an ABC-owned station, now it's an independent affiliate.
WFIL-TV/WPVI, Philadelphia was an independent ABC affiliate, but its former owners (Cap Cities) liked ABC so much they bought the company. 

[gregg75]

It's strange that a lot of these stations have been sold 5 or more times, but kept their networks.

I'll finish out Georgia

WMAZ 13 Macon CBS
WRDW 12 Augusta CBS

Augusta has another UHF station that almost qualifies, but they had a rough start (being UHF)
and went silent for a few years. WATU 26 NBC is now WAGT 26 NBC.

NBC allowed WJBF and WATU to cherry pick. Although WATU was NBC, The Today and Tonight
shows were on WJBF (ABC,NBC).

[KeithE4]

These started out as affiliates, but were later bought by/merged with the network they were affiliated with:
Chicago:  WBKB/WBBM 4/2 (CBS)
Philadelphia:  WFIL/WPVI 6 (ABC)
San Francisco:  KPIX 5 (CBS)
Dallas/Ft. Worth:  WBAP/KXAS 5 (NBC)

Others that have stayed "loyal" through the decades:
Dayton OH:  WHIO 13/7 (CBS)
Louisville KY:  WAVE 5/3 (NBC)
Champaign IL:  WCIA 3 (CBS)
Lafayette IN:  WFAM/WLFI 59/18 (CBS)
Ft. Wayne IN:  WINT/WANE 15 (CBS), WPTA 21 (ABC), WKJG/WISE 33 (NBC)
Evansville IN:  WFIE 62/14 (NBC)
Grand Rapids/Kalamazoo MI:  WKZO/WIMT 3 (CBS), WLAV/WOOD/WOTV/WOOD 7/8 (NBC), WZZM 13 (ABC), WUHQ 41 (ABC)
Jackson MI:  WILX 10 (NBC)
Traverse City/Cadillac MI:  WPBN 7 (NBC), WWTV 9 (CBS)
Des Moines IA:  KRNT/KCCI 8 (CBS), WHO 13 (NBC)
Quad Cities IL/IA:  WHBF 4 (CBS), WOC/KWQC 6 (NBC), WQAD 8 (ABC)
Quincy IL/Hannibal MO:  KHQA 7 (CBS), WGEM 10 (NBC)
Dallas TX:  WFAA 8 (ABC), plus the aforementioned WBAP/KXAS

[CdSull502]

From the Northeast---WJAR-TV Providence 1949 NBC
                     WTIC-TV/WFSB Hartford 1957 CBS (was an independent for a brief time after it
                     signed on)
                     WMUR-TV Manchester 1954  ABC
                     WMTW-TV Mt. Poland Spring / Portland 1954 ABC
                     WCSH-TV Portland 1953 NBC
                     WGAN-TV/WGNE Portland 1954 CBS         

[Scott Fybush]

More from the northeast:

Springfield MA
WWLP 22 (originally 61) - 1953, NBC

Utica NY
WKTV 2 (originally 13) - 1954, NBC

Syracuse NY
WSTM 3 (originally WSYR-TV 5) - 1950, NBC
WTVH 5 (originally WHEN-TV - 1948, CBS
WSYR-TV 9 (originally WNYS) - 1962, ABC

Rochester NY
WHAM-TV 13 (originally WOKR) - 1962, ABC

Buffalo NY
WIVB 4 (originally WBEN-TV) - 1948, CBS
WKBW 7 - 1958, ABC

Binghamton

WBNG 12 (originally WNBF-TV) - 1949, CBS
WIVT 34 (originally WBJA) - 1962, ABC

Elmira

WETM 18 (originally WSYE) - 1956, NBC
WENY-TV 36 - 1969, ABC

Burlington/Plattsburgh

WCAX 3 (originally WMVT) - 1954, CBS
WPTZ 5 (originally WIRI) - 1954, NBC
WVNY 22 - 1969, ABC

Erie PA
WICU 12 - 1949, NBC
WJET 24 - 1966, ABC
WSEE 35 - 1954, CBS

Pittsburgh
WTAE 4 - 1958, ABC
WPXI 11 (ex-WIIC) - 1957, NBC

Come to think of it, there have been no network shifts in Scranton/Wilkes-Barre, Harrisburg/Lancaster/York, or Altoona/Johnstown, either...

[Iowan]

All three TV stations from the Quad Cities area that signed on before 1970 are still with their networks:

1.  KWQC (NBC, 1949)
2.  WHBF (CBS, 1950)
3.  WQAD (ABC, 1963)

[Mike]

Bangor's WVII (originally WEMT) on Channel 7 has always been ABC since signing on in 1965.