A “sanctuary city” in the United States is one where the city protects illegal immigrants from certain practices, such as asking about a person’s legal status. The term “sanctuary city” has been cited in print since at least April 1985, when Cambridge, Massachusetts, voted to be a sanctuary city. The “sanctuary” was originally intended in the 1980s for political refugees fleeing civil wars in El Salvador and Guatemala. However, the “sanctuary city” concept accepts all immigrants, whether for political or for economic reasons.
 
   
Wikipedia: Sanctuary city
Sanctuary city is a term given to a city in the United States that follows certain practices that protect illegal immigrants. These practices can be by law (de jure) or they can be by habit (de facto). The term generally applies to cities that do not allow municipal funds or resources to be used to enforce federal immigration laws, usually by not allowing police or municipal employees to inquire about one’s immigration status. The designation has no legal meaning.

History of sanctuary cities
Cities in the United States began designating themselves as sanctuary cities during the 1980s. The policy was first initiated in 1979 in Los Angeles, to prevent police from inquiring about the immigration status of arrestees. The internal policy, “Special Order 40,” states: “Officers shall not initiate police action with the objective of discovering the alien status of a person. Officers shall not arrest nor book persons for violation of title 8, section 1325 of the United States Immigration code (Illegal Entry).” Some of the 31 American cities are Washington, D.C.; New York City (see also Illegal immigration in New York City); Jersey City; Los Angeles; San Francisco; Santa Ana; San Diego; San Jose; Oakland; Salt Lake City; El Paso; Houston; Detroit; Chicago; Minneapolis; Miami; Denver; Baltimore; Seattle; Portland, Oregon; New Haven; Somerville; Cambridge; Portland, Maine; and Tulsa. These cities have adopted “sanctuary” ordinances banning city employees and police officers from asking people about their immigration status.
 
9 April 1985, Boston (MA) Globe, “Cambridge votes to be a sanctuary” by Ross Gelbspan, Metro sec., pg. 1:
The Cambridge City Council voted last night to make Cambridge a “sanctuary city” and ordered city employees not to cooperate with federal agents seeking to deport refugees from El Salvador, Guatemala and Haiti.
 
Before the vote, the council heard testimony from sanctuary workers at Old Cambridge Baptist Church, from Beatriz Manz, an anthropology professor at Wellesley College, from a representative of Centro Presente, a refugee assistance organization in Cambridge, and from Richard Bell, an aide to US Sen. John Kerry (D-Mass.), as well as from several Haitians snd Salvadoran speakers.
 
Google News Archive
11 August 1985, The Courier (Prescott, AZ),  “Activists try for Washington sanctuary” (UPI), pg. 2A, col. 3:
In becoming a sanctuary city, local authorities refuse to cooperate with federal immigration authorities in rooting out undocumented immigrants and the church leaders harboring them.
 
Google News Archive
3 December 1985, Lodi (CA) News-Sentinel, “Funds may be cut off to sanctuary cities,” pg. 5, col. 1:
LOS ANGELES (UPI)—The INS western regional director flew to Washington Monday, vowing to try to persuade his superiors to cut off federal funds from Los Angeles and other cities that declare themselves sanctuaries for political refugees.
 
San Francisco (CA) Human Rights Commission
In 1989, San Francisco passed the Sanctuary City Administrative Code 12H, also known as the Sanctuary City Ordinance (“SCO”). The SCO prohibits the use of City funds or resources to assist Immigration and Customs Enforcement with arrests and/or the gathering or dissemination of information regarding the immigration status of an individual in San Francisco, unless it is mandated by federal or state law, warrant, or court decision. The SCO specifically states that City and County of San Francisco employees:

. Cannot ask about an individual’s immigration status;
. Cannot disclose information regarding an individual’s immigration status; and
. Cannot condition services based on an individual’s immigration status.
   
Los Angeles (CA) Times
Editorial
Sanctuary city? Not L.A.
It’s widely asserted that Los Angeles illegally shields undocumented immigrants from federal authorities. That is utterly false.
August 26, 2011
(...)
Even Wikipedia lists Los Angeles as a sanctuary city.
 
That’s widely believed. It’s also utterly false.
(...)
The idea of sanctuary cities dates to the 1980s, when thousands of people fleeing civil wars in El Salvador and Guatemala sought refuge in the United States. American involvement in those wars made the federal government reluctant to acknowledge the danger the refugees faced in their home countries, so churches and synagogues rallied to take them in and shield them from deportation. Some cities, including Los Angeles, joined that movement. In 1985, the City Council formally expressed its “opposition to the deportation of known law-abiding Central American refugees who have fled their homelands for the fear of losing their lives.” Even then, however, the council insisted that its support for those refugees should not be construed as “sanctioning the violation of any law or encouraging interference in law enforcement efforts.” At no point did the city government protect immigrants from federal authorities.