Editing Independent Subway System (section)

==Service letters==
As originally designed, the IND train identification scheme was based on three things: the Manhattan trunk line served (8th Avenue or 6th Avenue), the northern branch line served (Washington Heights, Grand Concourse/Bronx, or Queens Boulevard), and the service level (Express or Local). The 8th Avenue routes were A, C, and E. The 6th Avenue routes were B, D, and F. The A and B served Washington Heights. The C and D served the Grand Concourse. The E and F served Queens Boulevard via the 53rd Street Tunnel.<ref name=":0"/>

A single letter indicated an express service, while a double letter indicated local service. G was used for Brooklyn-Queens "Crosstown" service. H was used for any service on the extended Fulton Street (Brooklyn) line that did not originate in Manhattan.<ref name=":0">{{Cite web|url=http://www.nycsubway.org/wiki/Subway_FAQ:_Letter,_Number,_and_Color_Designation_Systems|title=Subway FAQ: Letter, Number, and Color Designation Systems|last=Brennan|first=Joseph|date=2012|website=www.nycsubway.org|access-date=November 27, 2016}}</ref>

The first designations were as follows:

{| class="wikitable"
|- valign="top"
|style="color:white; background-color:#{{rcr|NYCS|A}}"|A||style="color:white; background-color:#{{rcr|NYCS|A}}"|AA||Eighth Avenue – Washington Heights
|- valign="top"
| ||style="color:white; background-color:#{{rcr|NYCS|B}}"|BB||Sixth Avenue – Washington Heights
|- valign="top"
|style="color:white; background-color:#{{rcr|NYCS|C}}"|C||style="color:white; background-color:#{{rcr|NYCS|C}}"|CC||Eighth Avenue – Concourse
|- valign="top"
|style="color:white; background-color:#{{rcr|NYCS|D}}"|D|| ||Sixth Avenue – Concourse
|- valign="top"
|style="color:white; background-color:#{{rcr|NYCS|E}}"|E|| ||Eighth Avenue – Queens Boulevard
|- valign="top"
|style="color:white; background-color:#{{rcr|NYCS|F}}"|F|| ||Sixth Avenue – Queens Boulevard
|- valign="top"
|style="color:white; background-color:#{{rcr|NYCS|G}}"|G||style="color:white; background-color:#{{rcr|NYCS|G}}"|GG||Brooklyn-Queens Crosstown
|- valign="top"
| ||style="color:white; background-color:#{{rcr|NYCS|S}}"|HH||Fulton Street
|- valign="top"
| S|| ||Special
|}
Virtually all possibilities were used at one time or another, either in regular service or as brief special routes.<ref name="nycsubway.org"/> The "G" single-letter service was used for {{NYCS|G}} service to [[IND World's Fair Line|World's Fair Station]] in 1939.

The final pre-[[Chrystie Street Connection]] service is shown here; for more details, see the individual service pages. Terminals shown are the furthest the service reached.<ref name=":0" />
{| class="wikitable"
!
!Line
!Routing
!Notes
|-
|[[A (New York City Subway service)|A]]||Washington Heights Express||[[Inwood–207th Street (IND Eighth Avenue Line)|207th Street]] – [[Ozone Park–Lefferts Boulevard (IND Fulton Street Line)|Lefferts Boulevard]] or [[Far Rockaway–Mott Avenue (IND Rockaway Line)|Far Rockaway]] or [[Rockaway Park–Beach 116th Street (IND Rockaway Line)|Rockaway Park]] (via [[IND Eighth Avenue Line|Eighth Avenue]])||still in use
|-
|[[AA (New York City Subway service)|AA]]||Washington Heights Local||[[168th Street (IND Eighth Avenue Line)|168th Street]] – [[World Trade Center (IND Eighth Avenue Line)|Hudson Terminal]] (via [[IND Eighth Avenue Line|Eighth Avenue]])||became [[K (Eighth Avenue Local)|K]] (no longer operated)
|-
|[[BB (New York City Subway service)|BB]]||Washington Heights Local||[[168th Street (IND Eighth Avenue Line)|168th Street]] – [[34th Street–Herald Square (IND Sixth Avenue Line)|34th Street]] (via [[IND Sixth Avenue Line|Sixth Avenue]])||became [[B (New York City Subway service)|B]] (now goes from [[Bedford Park Boulevard (IND Concourse Line)|Bedford Park Boulevard]] to [[Brighton Beach (BMT Brighton Line)|Brighton Beach]])
|-
|[[C (New York City Subway service)|C]]||Bronx Concourse Express||[[Norwood–205th Street (IND Concourse Line)|205th Street]] – [[Utica Avenue (IND Fulton Street Line)|Utica Avenue]] (via [[IND Eighth Avenue Line|Eighth Avenue]])||no longer operated; combined into A and D trains
|-
|[[CC (New York City Subway service)|CC]]||Bronx Concourse Local||[[Bedford Park Boulevard (IND Concourse Line)|Bedford Park Boulevard]] – [[World Trade Center (IND Eighth Avenue Line)|Hudson Terminal]] (via [[IND Eighth Avenue Line|Eighth Avenue]])||became [[C (New York City Subway service)|C]] (now goes from [[168th Street (IND Eighth Avenue Line)|168th Street]] to [[Euclid Avenue (IND Fulton Street Line)|Euclid Avenue]])
|-
|[[D (New York City Subway service)|D]]||Bronx Concourse Express||[[Norwood–205th Street (IND Concourse Line)|205th Street]] – [[Coney Island–Stillwell Avenue (BMT West End Line)|Coney Island]] (via [[IND Sixth Avenue Line|Sixth Avenue]] and [[IND Culver Line|Culver Line]])||still in use, though trains now use the [[BMT West End Line|West End Line]]
|-
|[[E (New York City Subway service)|E]]||Queens–Manhattan Express||[[Jamaica–179th Street (IND Queens Boulevard Line)|179th Street]] – [[World Trade Center (IND Eighth Avenue Line)|Hudson Terminal]] or [[Rockaway Park–Beach 116th Street (IND Rockaway Line)|Rockaway Park]] (via [[IND Eighth Avenue Line|Eighth Avenue]] and [[IND Houston Street Line|Houston Street]])||still in use, though all trains go from [[Jamaica Center–Parsons/Archer (Archer Avenue Lines)|Jamaica Center]] to Hudson Terminal (now called World Trade Center)
|-
|[[F (New York City Subway service)|F]]||Queens–Manhattan Express||[[Jamaica–179th Street (IND Queens Boulevard Line)|179th Street]] – [[World Trade Center (IND Eighth Avenue Line)|Hudson Terminal]] or [[Coney Island–Stillwell Avenue (IND Culver Line)|Coney Island]] (via [[IND Sixth Avenue Line|Sixth Avenue]])||still in use, though all trains go to Coney Island or [[Kings Highway (IND Culver Line)|Kings Highway]]
|-
|[[GG (New York City Subway service)|GG]]||Queens Brooklyn Local||[[Forest Hills–71st Avenue (IND Queens Boulevard Line)|Forest Hills]] – [[Church Avenue (IND Culver Line)|Church Avenue]] (via [[IND Crosstown Line|Crosstown Line]])||became [[G (New York City Subway service)|G]], though all trains [[short turn]] at [[Court Square (IND Crosstown Line)|Court Square]]
|-
|[[HH (Court Street Shuttle)|HH]]||Court Street Shuttle||[[Court Street (IND Fulton Street Line)|Court Street]] – [[Hoyt–Schermerhorn Streets (IND Fulton Street Line)|Hoyt–Schermerhorn Streets]]||no longer operated, but the trackage is used for moving trains in and out of the [[New York Transit Museum]], located in the Court Street station
|-
|[[HH (Rockaway Local)|HH]]||Rockaway Local||[[Euclid Avenue (IND Fulton Street Line)|Euclid Avenue]] – [[Rockaway Park–Beach 116th Street (IND Rockaway Line)|Rockaway Park]] or [[Far Rockaway–Mott Avenue (IND Rockaway Line)|Far Rockaway]]||became [[H (New York City Subway service)|H]], then [[Rockaway Park Shuttle|S]], though now, all trains only go to Rockaway Park
|}

After the Chrystie Street Connection opened, the original IND Service Letter scheme was gradually abandoned.  All lines, whether local or express, now use a single letter, and only the 8th Avenue/6th Avenue distinction (A, C, E vs. B, D, F) has been maintained.<ref name="nycsubway.org"/> Following consolidation under city ownership, the numbered routes of the former [[Brooklyn–Manhattan Transit Corporation|BMT system]] were also gradually relabeled to letters for consistency with the IND system.