The History of Chicago / Evanston Telephone Exchanges Including Their Two-Letter Codes and Meanings.

Contrary to popular belief, there were no central office prefixes in the beginning. To place a call on June 26, 1878, when the Bell-licensed Chicago Telephonic Exchange first opened, the subscriber merely told the operator the name and address of the party desired.

Telephone switchboard operator, Washington Island, Wisconsin, 1915.

For purposes of identification, the original telephone switchboard at 125 LaSalle St. was known as the Central office. Two more offices soon opened and were called the Halsted Street branch and the Canal Street branch.

By 1883, these three central offices had grown to 11, and around that time the Bell System-affiliated Chicago Telephone Company (formed in 1881) began to refer to most of them by number. Thus, the switchboard at 125 LaSalle St. became known as the № 2 office. By then, too, subscribers were requested to call by number rather than by name.

Chicago telephone switchboard in the 1880s. (photo via Illinois Bell)

The initial digit of the phone number generally indicated the telephone central office; that is, the subscriber who had “3123” as the call number was served from № 3 office at Chicago Ave. and Clark St. The three offices lying just outside the city limits had no numerical designation and were known as Stock Yards, Oakland and Ravenswood. In 1889, Stock Yards was changed to Yards and Ravenswood to Lake View. In that same year, telephone growth brought about the first use of 5-digit numbers, the Oakland series running from 9800 to 10,999 and the Lake View series from 12,001 to 12,499. This first call number system was inflexible, however, because it allowed little latitude for growth.

By 1892, on the eve of the opening of the World’s Columbian Exposition, it became apparent that the city was rapidly outgrowing the old numbering scheme, and in that year the change to a system of combined prefix and number was made. Beginning February 15, a subscriber served from № 3 office had his/her number change from “3123” to “North 123.”  The entire list of changes:

Old Designation                   Serving #s                          Changed to

№ 2 office                             1 to 2999                             Main 1 to Main 2999

№ 3                                        3001 to 3999                       North 1 to North 999

№ 4 & 5                                 4000 to 5399                        Main 4000 to Main 5399

№ 7                                        7001 to 7999                       West 1 to West 999

№ 8                                        8001 to 8999                       South 1 to South 999

№ 9                                        9001 to 9499                       Canal 1 to Canal 499

Yards                                     9500 to 9799                       Yards 500 to Yards 799

Oakland                                 9800 to 10,999                    Oakland 800 to Oakland 999

Lake View                             12,001 to 12,499                  Lake View 1 to Lake View 499

Telephone numbers, therefore, started using the central office name as the prefix. This second system remained in effect for nearly 30 years.

Early switchboard operator, 1880s.

In June 1921, Illinois Bell Telephone Company (formed in December 1920 from the merger of Chicago Telephone Company and the Illinois properties of Central Union Telephone Company) adopted the citywide 3-letter 4-number plan, effective with the delivery of the October telephone directory. At that time, all phone numbers with less than four digits were changed to add zeros ahead of the number to make four numerals in all cases (for example, “NORth 0029”).

Certain names, such as “Monticello,” were replaced because their numerical equivalents, in this case, “666,” conflicted with other existing offices, like “Monroe.” As a result, “Monticello” became “Juniper.” This change was necessary for the launch of automatic dial service, first introduced in Chicago with the cutover of “CENtral” prefix (in the Franklin Building at 315 W. Washington St.) on June 9, 1923.

The fourth alteration in Chicago’s calling plan was the conversion to 2 letters and 5 numbers across the city on September 18, 1948 (for instance, “CEntral 6-1234”). As with the implementation of central office prefixes in 1892, the change to the 2-letter 5-number plan was necessary to provide additional telephone numbers required by the enormous demand for phone service after World War II.

The following is the complete list of Chicago and Evanston central office exchange names and their corresponding prefixes, adopted in 1948.

Rotary Dial

Two 17-year-old teenagers were baffled by a rotary phone. A must-watch video.

Telephone operators, 1950s.

This system allowed for additional prefix equivalents without the invention of new exchange names.

ABerdeen........... AB 4

ALbany............. AL 2

AMbassador......... AM 2

ANdover............ AN 3

ARdmore............ AR 1

ARmitage........... AR 6

ATlantic........... AT 5

AUstin............. AU 7

AVenue............. AV 2,3&6

BAyport............ BA 1

BElmont............ BE 5

BErkshire.......... BE 7

BEverly............ BE 3&8

BIshop............. BI 2&7

BIttersweet........ BI 8

BOulevard.......... BO 8

BRiargate.......... BR 4
BRoadway........... BR 3,4&5

BRunswick.......... BR 8

BUckingham......... BU 1

BUtterfield........ BU 8

CAlumet............ CA 5

CAnal.............. CA 6

CApitol............ CA 7

CAthedraL.......... CA 8

CEdarcrest......... CE 3

CEntral............ CE 6

CHesapeake......... CH 3

CLiffside.......... CL 4

COlumbus........... CO 1

COmmodore.......... CO 4

COrnelia........... CO 7

CRawford........... CR 7

DAnube............. DA 6

DAvis.............. DA 8

DEarborn........... DE 2

DElaware........... DE 7

DIckens............ DI 2

DIversey........... DI 8

DOrchester......... DO 3

DRexel............. DR 3

EAstgate........... EA 7

EDgewater.......... ED 4

ELmdrive........... EL 6

ENglewood.......... EN 4

ESsex.............. ES 5

EStebrook.......... ES 8&9

EVerglade.......... EV 4

FAirfax............ FA 4

FInancial.......... FI 6

FIre............... FI 7

FRanklin........... FR 2

FRontier........... FR 4&6
FUlton............. FU 5

GArden............. GA 4
GLadstone.......... GL 5

GRaceland.......... GR 2&7

GReenleaf.......... GR 5

GRovehill.......... GR 6

HArrison........... HA 7

HAymarket.......... HA 1

HEmlock............ HE 4&6

HIlltop............ HI 5

HOllycourt......... HO 5

HUdson............. HU 3,7&8

HUmboldt........... HU 6&9

HYde Park.......... HY 3

INdependence....... IN 3

INterocean......... IN 8

IRving............. IR 8

JUniper............ JU 3&8

KEdzie............. KE 3

KEnwood............ KE 6&8

KEystone........... KE 3&9

KIldare............ KI 5

LAfayette.......... LA 1,2&3

LAkeview........... LA 5&8

LAwndale........... LA 1&2

LIncoln............ LI 9

LIvingston......... LI 8

LOngbeach.......... LO 1
LUdlow............. LU 2&5

MAnsfield.......... MA 6

MErrimac........... ME 7

MIchigan........... MI 2

MIdway............. MI 3
MItchell........... MI 6

MOhawk............. MO 4

MOnroe............. MO 6

MUlberry........... MU 5

MUseum............. MU 4

NAtional........... NA 2&5

NEvada............. NE 2&8

NEwcastle.......... NE 1

NOrmal............. NO 7

OAkland............ OA 4

OFficial........... OF 3
ORchard............ OR 3&6

PAlisade........... PA 5

PEnsacola.......... PE 6

PLaza.............. PL 2

POlice............. PO 5

POrtsmouth......... PO 7
PRescott........... PR 9

PRospect........... PR 6&8

PUllman............ PU 5

RAdcliffe.......... RA 3

RAndolph........... RA 6&7

RAvenswood......... RA 8

REgent............. RE 1&4

REliance........... RE 5

REpublic........... RE 7

ROckwell........... RO 2

ROdney............. RO 3

ROgers Park........ RO 1&4

SAcramento......... SA 2

SAginaw............ SA 1

SEeley............. SE 3&8

SHeldrake.......... SH 3

SOuth Chicago...... SO 8

SOuth Shore........ SO 8

SPaulding.......... SP 2

SPring............. SP 4,5&7

STate.............. ST 1&2

STewart............ ST 3

SUnnyside.......... SU 4

SUperior........... SU 7

TAylor............. TA 9

TRiangle........... TR 3&4

TUxedo............. TU 9

UNderhill.......... UN 7
UNiversity......... UN 4,6&9

UPtown............. UP 8

VAn Buren.......... VA 6

VIctory............ VI 2

VIncennes.......... VI 6

VIrginia........... VI 7

WAbash............. WA 2

WAgner............. WA 4

WAlbrook........... WA 5

WAterfall.......... WA 8

WEather............ WE 4

WEbster............ WE 9

WEllington......... WE 5

WEntworth.......... WE 6

WHitehall.......... WH 3&4

YArds.............. YA 7

The fifth and final telephone number scheme began with the conversion to All Number Calling (ANC) on September 11, 1960.  Despite some early opposition from individuals and businesses who wanted to retain their beloved exchange prefixes, this evolutionary process was finally completed in 1977.

At that point, the Chicago alphabetical directory (White Pages) showed all local numbers in the city to be in the now-familiar 7-digit format still in use today (such as “236-1234”).

Exchange names continued appearing in some Chicago Yellow Pages and advertisements into the 1980s.

In the original North American Numbering Plan of 1947, all of the Chicago area was covered by area code 312, the rest of northern Illinois was 815, central Illinois was 217, and southern Illinois was 618.

Reasons why people tend to remember their first telephone number, no matter how old they are.

Safety and Security: Parents, teachers, and community safety programs emphasize the importance of children memorizing their home telephone numbers at a young age. This was done as a safety measure so that children can contact their parents or guardians in case of an emergency or if they get lost. This early and frequent repetition can make the number stick in a person’s memory, possibly forever.

Repetition and Usage: The first telephone number that one learns is often used repeatedly over a long period of time. This frequent repetition can engrain the number in one’s memory.

Significance: The first telephone number is often associated with one’s childhood home or a significant period in one’s life, which can make the number more memorable.

Necessity: In the past, before the advent of smartphones and digital contact lists, people had to memorize or write down important phone numbers. This necessity could have contributed to the long-term retention of these numbers.

However, the need to memorize phone numbers has significantly decreased with the advent of smartphones and digital contact lists. Many people today do not remember phone numbers because they rely on their devices to store and dial them.

ADDITIONAL READING: The Chicago Telegraph arrived in 1848. It becomes the eastern terminus of “Western” communication.

Compiled by Dr. Neil Gale, Ph.D.