April 12, 2002 – A federal court sided with the Center when it ruled that a planned expansion of Fort Huachuca was dewatering the San Pedro River and jeopardizing the existence of several endangered species in the process.
May 7, 2003 – Rep. Rick Renzi, R-Ariz., attached a rider to H.R. 1835, the National Security Readiness Act of 2003, that would exempt military gardens, lawns, pools, and golf courses from environmental laws — and would exempt Fort Huachuca from responsibility for groundwater pumping. The rider, first introduced in 2002 by Rep. Jim Kolbe, had already once been defeated after opposition by the Center and others.
August 26, 2003 – The Center, along with 23 other conservation groups, appealed to Governor Janet Napolitano to help save the San Pedro River from the Renzi rider.
September 1, 2003 – The Center wrote a letter to Rep. Renzi, detailing the problems his rider posed to the San Pedro River and the species that depend on it.
November 7, 2003 – Despite opposition from the Center and allies, the Renzi rider passed Congress with the help of Sen. John McCain. It remains the single largest impediment to the Center's legal work to protect the San Pedro from the overpumping of groundwater.
September 7, 2004 – The Center filed a complaint with the Arizona attorney general to stop the Arizona Department of Water Resources' false suggestion to consumers and lenders that the San Pedro's water supply was adequate to support development.
March 17, 2005 – The Center, along with the Maricopa Audubon Society, filed a notice of intent to sue the U.S. Department of Defense and the U.S. Fish and Wildlife Service for jeopardizing the San Pedro River and its dependent endangered species by ignoring recommendations from a 2002 biological opinion.
April 5, 2005 – The Center, represented by Earthjustice, filed a lawsuit against the Veterans Administration, the Federal Housing Administration, and the Small Business Administration for failing to examine the environmental impact of developments relying on water from the San Pedro.
June 1, 2005 – Along with the Maricopa Audubon Society, the Center filed a lawsuit against Fort Huachuca, the Department of Defense, and the Fish and Wildlife Service for approving rapid expansions of Fort Huachuca that exceeded what was recommended as sustainable in a 2002 biological opinion.
June 6, 2005 – Data from groundwater monitoring wells at Fort Huachuca revealed that excessive pumping in the area was causing groundwater levels to drop and was directly affecting the San Pedro's base flow.
July 9, 2005 – For the first time in recorded history, the San Pedro River ran dry at the Charleston gage near Fort Huachuca.
July 20, 2005 – As a result of the Center's April 2005 lawsuit, Fort Huachuca was forced to release a previously censored report showing that excessive local groundwater pumping was directly affecting the San Pedro River.
March 1, 2006 – In a successful resolution to the Center's June 2005 lawsuit, Fort Huachuca announced that it would reinitiate consultation with the Fish and Wildlife Service in an effort to fulfill its obligations to protect the San Pedro River and its species.
April 25, 2006 – The Center came out against a planned sale of a rail line running through the San Pedro Riparian National Conservation Area that would seriously damage the river corridor and bring unsustainable growth to Naco, Arizona and Naco, Mexico.
July 12, 2006 – The planned sale of the San Pedro River railroad, which would have allowed hazardous materials to be transported along the river's banks, was halted when the purchase offer was withdrawn.
July 5, 2007 – For the third straight year, the San Pedro River stream flow dried up at the Charleston gage near Fort Huachuca.
February 28, 2008 – The Center filed a notice of intent to sue Pinal Country to stop the ongoing destruction of pristine habitat after the country erroneously used an “emergency” clause to illegally develop an area on the lower San Pedro.
March 4, 2008 – The Center filed a formal Clean Water Act violation against Pinal County for its ongoing destruction of rare habitat along the lower San Pedro River.
April 25, 2008 – Bureau of Land Management documents revealed that the Department of Homeland Security had ignored warnings of damage to the San Pedro River prior to exempting the border wall across the San Pedro Riparian National Conservation Area from all environmental laws.
June 4, 2008 – Along with the Maricopa Audubon Society and the Tucson Audubon Society, the Center filed a lawsuit against Pinal County to stop ongoing ecological damage to the Bureau of Land Management's lower San Pedro River conservation area after the agency began illegally dredging and filling in the river.
February 10, 2010 – The Center's June 2008 lawsuit against Pinal County was settled when the Army Corps of Engineers cited the county for its illegal activities and the Bureau of Land Management agreed to cease dredging and filling activities that were damaging the San Pedro watershed.
January 26, 2011 – The Center released a hydrology study showing the extent of the San Pedro's danger from the effects of Fort Huachuca and city of Sierra Vista groundwater pumping. Well-water levels were already declining near the river at the Fort's eastern border, the study revealed.
May 31, 2011 – In response to a Center lawsuit, a federal judge rejected the latest plan by the Army and U.S. Fish and Wildlife Service aimed at preventing damage to the San Pedro River to serve Fort Huachuca. The judge said the Army and the Fish and Wildlife Service had relied on a “legally flawed” plan that didn't protect the San Pedro River and failed to properly analyze groundwater pumping's effect on imperiled species.
February 2014 – The Center filed a cease-and-desist notice with the Federal Aviation Administration and Arizona's Department of Transportation to stop spending money for the construction of a new taxiway at the Sierra Vista Muni-Libby Airport. Initial work to support the taxiqway had already begun without an analysis of environmental harm, such as to the San Pedro River and its wildlife, including the southwestern willow flycatcher, Huachuca water umbel, desert pupfish, loach minnow, spikedace, yellow-billed cuckoo and Mexican garter snake.