North American metro rail, subway & light rail systems - including subways, els, peoplemovers, subte networks:

Atlanta
Baltimore
Boston
Buffalo
Calgary
Charlotte
Chicago
Cincinnati
Cleveland
Dallas
Denver
Detroit

Mexico City
Miami
Milwaukee
Minneapolis/St. Paul
Monterrey
Montréal
Morgantown
New Orleans
New York City
Norfolk
Northern New Jersey (Newark)

SUBWAYS & LIGHT RAIL
in the U.S.A.
-- The Book! --
Vol. 1: East Coast

Click here for more info!

SUBWAYS & LIGHT RAIL
in the U.S.A.
-- The Book! --
Vol. 2: The West

Click here for more info!

SUBWAYS & LIGHT RAIL
in the U.S.A.
-- The Book! --
Vol. 3: Midwest & South

Click here for more info!

URBAN RAIL in CANADA

Cities with metro & light rail projects - planned or under construction:

Austin | Hamilton | Mississauga | Omaha | Québec | Santa Ana, Orange County | Santiago de los Caballeros

+ Other current projects under construction in North America:

Calgary - Green Line from Event Centre to Shepard

Chicago - Red Line south extension from 95th Street/Dan Ryan to 130th Street

Edmonton - Valley Line West from downtown to Lewis Farms; Capital Line south extension from Century Park to Ellerslie Road

Honolulu - Skyline east extension from Kahauiki into the city centre

Los Angeles - LAX People Mover; Purple Line extension to Santa Monica; East San Fernando Valley Light Rail

Mexico City - line 12 from Mixcoac to Observatorio

Minneapolis/St. Paul - Southwest extension from Target Field to Eden Prairie

Monterrey - Monorail lines 4 and 6

Montréal - Blue Line northeast extension from Saint-Michel to Anjou; REM Airport branch

New York City - 2nd Avenue Subway extension north from 96th Street to 125th St & Park Ave

Ottawa - Line 1 west and east extensions

St. Louis - MidAmerica St. Louis Airport extension

San José - BART extension from Berryessa to Santa Clara; light rail extension from Alum Rock to Eastridge

Santo Domingo - Line 1 north extension

Toronto - new Ontario Line; Line 1 north extension from Finch to High Tech (Langstaff); Line 2 east extension from Kennedy to Scarborough; Line 5 west extension from Mount Dennis to Renforth

Vancouver - Millennium Line west extension from VCC-Clark to Arbutus; Expo Line east extension from King George to Langley

Washington D.C. - new Purple Line (tangential light rail line in Maryland)

Cincinnati's Abandoned Subway

Heritage & classic streetcar systems with regular daily service:

El Paso | Little Rock | Memphis | New Orleans | Philadelphia | San Francisco | Tampa

List of rail transit systems in the United States at Wikipedia

NYC Subway Resources is the site you need for anything related to North America not included in UrbanRail.Net (incl. many good maps)

ERA (Electric Railroaders’ Association - USA)

Alamys.org - Association of Latin American Metros and Subways

Jon Bell's Transit Pages include links to many US mass transit systems

The Transport Politic - Urban Rail Projects in North America