Plains All American Pipeline (NYSE: PAA) is a publicly traded Master limited partnership in the oil pipeline transportation, marketing, and storage business in the United States, liquefied petroleum gas business in Canada, and natural gas storage business in Michigan and Louisiana. It owns about 37 million barrels (5,900,000 m³) of terminal and storage capacity and 15,000 miles (25,000 km) of crude oil pipelines.

Its parent company, Plains GP Holdings, L.P. NYSE: PAGP was formed as a holding company in 2013 to own and manage Plains American Pipeline. In 2014, Plains GP ranked 70 on the Fortune 500.

The company itself is headquartered in Three Allen Center in Downtown Houston, Texas; was traded in 1993; and grew through investment, originally in the Cushing Terminal in Cushing, Oklahoma and mostly acquisition, aimed at improving the transmission of oil to the Midwest. Plains Midstream Canada, an indirect subsidiary of Plains All American Pipeline, does business in 5 provinces in Canada and more than 40 U.S. states.

Major acquisitions include:

According to the EPA and U.S. Justice Department, Plains All-American Pipeline has had 11 serious crude oil spills in five states that included: Texas, Louisiana, Oklahoma, Kansas, and California. Between June 2004 and September 2007, more than 273,000 gallons of crude oil were discharged from various pipelines owned by Plains All-American Pipeline. According to the EPA, some of that oil ended up in rivers, lakes, and oceans. In 2010, the company reached a settlement with the EPA for a $3.25 million civil penalty for violating the Clean Water Act. The company also agreed to spend $41 million to upgrade more than 10,000 miles of crude oil pipelines.

One of the largest land-based oil spills in North America, the Little Buffalo oil spill occurred on April 29, 2011. The Rainbow Pipeline system, owned by Plains Midstream Canada, ruptured, spilling 28,000 barrels of oil in a fairly isolated stretch of boreal forest in northern Alberta, about four miles from the nearest homes in Little Buffalo, Alberta. It was reported to be the largest oil spill in Alberta in 36 years. It was also the second spill in Alberta within a two-week period that year. The local school was closed following the oil spill due to concerns about the effects of fumes.

Heavy rains in early June 2012 caused a leak on a Plains Midstream Canada 46-year-old pipeline at Jackson Creek, a tributary of the Red Deer River (Alberta) which spilled approximately 1,000-3,000 barrels (160,000-475,000 litres) of light sour crude into the Red Deer River.

In 2013, Alberta's Energy Resource Conservation Board (ERCB) issued a reprimand to Plains Mainstream for operational failures in connection with the oil spill. Plains Midstream Canada ULC was charged with three counts of violating environmental protection laws with possible fines of $1.5M if found guilty.

On May 19, 2015, a pipeline operated by Plains All American Pipeline ruptured north-west of Santa Barbara, California,. Within 24 hours, oil had polluted approximately nine miles of the Santa Barbara coast . The spill shut down the popular El Capitan Beach and Campground just prior to the beginning of the summer high season (Memorial Day weekend). Most recent estimates of the spill have risen to over 105,000 U.S. gallons (2,500 barrels). More than 20,000 U.S. gallons (480 barrels) of crude oil is estimated to have spilled into the ocean. The United States House Committee on Energy and Commerce opened an investigation into the oil spill on June 25, 2015 to gather information on maintenance of the line; corrosion management; and process of incident-reporting. According to federal regulations, companies are required to National Response Center and report the release of hazardous-material "at the earliest practicable moment." According to preliminary findings of the federal Pipeline and Hazardous Materials Safety Administration released in June, corrosion had worn a pipeline section to less than an inch thick. California Governor's Office of Emergency Services (CalOES) director Mark S. Ghilarducci testified at the state legislative hearing on June 25 that it appeared that Plains All American did not meet criteria for prompt notification. By June 2015 the cost of cleanup rose to USD$92 million. Santa Barbara County firefighters were among the first to discover the spill on May 18, 2015 and they "built a rim of rocks to prevent oil from running to the shoreline." The Coast Guard received the first call about the spill at 12:39 p.m. on May 18, 2015. The United States Environmental Protection Agency (EPA) and the U.S. Coast Guard formed the Unified Command to respond to the spill.

According to the California Department of Fish and Wildlife's Office of Spill Prevention and Response, OSPR crews were among the first responders of the crude oil spill. By June 22, 2015 they reported that,

"Of the estimated 101,000 gallons of crude discharged into the environment, some 21,000 gallons reached the Pacific Ocean. A Unified Command including OSPR leadership was established in Santa Barbara to coordinate cleanup and recovery operations. As of June 22, operations continue with the focus shifting from cleanup to environmental restoration.

OSPR uses social media including Twitter and Facebook via calspillwatch to report updates on oil spills.