The concept of sister city contingency plans was established in 1983 by the Joint Response Team (JRT). Recognizing that chemical emergencies affect the local community first, JRT members agreed that subsequent planning efforts would be needed for the 28 sister cities – 14 in Mexico and the adjacent 14 in the United States – that could be affected by a major hazardous substance release. The sister city contingency plan program was created to meet that need. Under the Border 2012 Program, a 15th Sister-City Pair or Tri-National Plan was recognized: The Tohono O'Odham Nation, State of Arizona and Sonoyta, Sonora, Mexico. In addition, under the Border 2012 Program, the sister cities of El Paso, Texas and Cuidad Juárez, Chihuahua also included Sunland Park, New Mexico and the Ysleta del Sur Pueblo into the sister-city plan, also becoming a Tri-National Plan.

The 15 Sister City Plans as recognized under the Border 2020 Program:

Region 9 Sister-City Plans:

• San Diego, California - Tijuana, Baja California (Updated 2013)
• Calexico (Imperial County), California - Mexicali, Baja California (Signed 2005, currently being updated)
• Yuma-San Luis, Arizona - San Luis Rio Colorado, Sonora (Signed 2000, currently being updated)
• Nogales, Arizona - Nogales, Sonora (Signed  2005, currently being updated)
• Naco (Cochise County), Arizona - Naco, Sonora (Signed 2002, currently being updated)
• Douglas, Arizona - Agua Prieta, Sonora (Signed 2001, currently being updated)
• Tohono O'Odham Nation - State of Arizona - Sonoyta, Sonora, Mexico (Pending approval of plan)

Region 6 Sister-City Plans:

• Columbus, New Mexico - Puerto Palomas, Chihuahua (Signed 2002)
• El Paso, Texas - Cuidad Juárez, Chihuahua - Sunland Park, New Mexico - Ysleta del Sur Pueblo (Signed 2007, Updated 2009)
• Presidio, Texas - Ojinaga, Chihuahua (Signed 2004, Updated 2013)
• Del Rio, Texas - Cuidad Acuña, Coahuila (Signed 2001, Updated 2013)
• Eagle Pass, Texas - Piedras Negras, Coahuila (Signed 1998, Updated 2013)
• Laredo, Texas - Nuevo Laredo, Tamaulipas (Signed 1998)
• McAllen, Texas - Reynosa, Tamaulipas (Signed 2000)
• Browsnville, Texas - Matamoros, Tamaulipas (Signed 2002, Pending final signatures by parties)

• 2013 San Diego - Tijuana Sister City Plan (English) (PDF)(72 pp, 796 K)
• Binational Prevention and Emergency Response Plan Between San Luis, Arizona and San Luis Rio Colorado, Sonora (PDF)(56 pp, 1 MB, 2/25/2000)
• Binational Prevention and Emergency Response Plan Between Nogales, Arizona and Nogales, Sonoara (PDF)(77 pp, 4 MB, 7/2005)
• Binational Prevention and Emergency Response Plan Between Cochise County, Arizona and Naco, Sonora (PDF)(116 pp, 3 MB, 10/4/2002)
• Binational Prevention and Emergency Response Plan Between Douglas, Arizona and Agua Prieta, Sonora (PDF)(52 pp, 232 K, 11/9/2001)
• Binational Prevention and Emergency Response Plan Between Imperial, California and the City of Mexicali, Baja California (PDF)(130 pp, 3 MB, 5/2005)
• 2002 Columbus-Palomas Sister City Plan (English) (PDF)(54 pp, 2 MB)
• 2002 Columbus-Palomas Sister City Plan (Spanish) (PDF)(51 pp, 3 MB)
• 2009 El Paso - Cuidad Juarez Sister City Plan - Sunland Park - Ysleta del Sur (English) (PDF)(16 pp, 1 MB)
• 2009 El Paso - Cuidad Juarez Sister City Plan - Sunland Park - Ysleta del Sur (Spanish) (PDF)(15 pp, 401 K)
• 2013 Presidio-Ojinaga Sister City Plan (English) (PDF)(61 pp, 1 MB)
• 2013 Presidio-Ojinaga Sister City Plan (Spanish) (PDF)(70 pp, 2 MB)
• 2013 Del Rio - Cuidad Acuna Sister City Plan (english) (PDF)(43 pp, 10 MB)
• 2013 Del Rio - Cuidad Acuna Sister City Plan (Spanish) (PDF)(43 pp, 10 MB)
• 2013 Eagle Pass - Piedras Negras Sister City Plan (English) (PDF)(49 pp, 11 MB)
• 2013 Eagle Pass - Piedras Negras Sister City Plan (Spanish) (PDF)(49 pp, 12 MB)
• 1998 Laredo-Nuevo Laredo Sister City Plan (English) (PDF)(60 pp, 3 MB)
• 1998 Laredo-Nuevo Laredo Sister City Plan (Spanish) (PDF)(65 pp, 4 MB)
• 2000 McAllen - Reynosa Sister city plan (English) (PDF)(67 pp, 4 MB)
• 2000 McAllen - Reynosa Sister city plan (Spanish) (PDF)(71 pp, 3 MB)
• 2002 Brownsville - Matamoros Sister City Plan (English) (PDF)(56 pp, 13 MB)
• 2002 Brownsville - Matamoros Sister City Plan (Spanish) (PDF)(61 pp, 3 MB)