In 1990, erosion led to the closure of a 0.75-mile section of the road between Cortland Place and Porter Street. This touched off a decades-long dispute between people who wanted the road repaired and those who wanted to keep the portion in Rock Creek Park free of automobile traffic. In 2017, that portion of Klingle Road became Klingle Valley Trail, reserved for hikers and bicyclists.
The valley forms the boundary between the Woodley Park neighborhood to the south and the Cleveland Park neighborhood to the north. A small stream, usually called Klingle Creek (but sometimes the Klingle Tributary), flows through it, and empties into Rock Creek. Much of the valley is administered by the National Park Service as a part of Rock Creek Park. The mouth of the valley joins the mouth of another narrow valley occupied by Porter Street.
Formerly Klingle Ford Road, Klingle Road became a public roadway in 1839, but only later was named Klingle. The road is named for Joshua Pierce Klingle, the nephew of Pierce Mill owner Joshua Pierce and was originally known as Klingle's Road. Klingle, who was adopted by Pierce when his parents died, inherited Pierce's land upon his death and in 1891 sold a large portion of it to the federal government for the creation of Rock Creek Park.
In 1885, the Klingle Road right-of-way was deeded to the City for use as a public highway. Five years later, when Congress authorized the creation of Rock Creek Park, Klingle formed the rough southern border of the new park. Along with Peirce Mill and Military Roads, it was the only roads that spanned the park north of the National Zoological Park.
In 1913, the city generated a plan to straighten and widen the street as Klingle Parkway, connecting Beach Drive and Reno Road. Before World War I, the road was used by farmers to bring grain to Peirce Mill.
Rock Creek Park retains a high degree of integrity that reflects the development of this public landscape between 1791 and 1941. In 1917, the Board of Control commissioned the firm of Frederick Law Olmsted, Jr., and his half-brother John C. Olmsted to prepare a planning study for the future development of Rock Creek Park. The resulting report, completed in 1918, became the seminal planning document for the planning and expansion of Rock Creek Park. Its first sentence boldly declared the credo that "The dominant consideration, never to be subordinated to any other purpose in dealing with Rock Creek Park, is the permanent preservation of its wonderful natural beauty, and the making of that beauty accessible to people without spoiling the scenery in the process." The Olmsted Plan for Rock Creek Park was adopted in 1919 and has remained a vital management document ever since. Certain roads were designated for vehicular use. Klingle Road, although not a part of Rock Creek Park, has served DC historically as a public road that provides public vehicular access to this urban treasure, Rock Creek Park.
The road network was a popular addition to the park because it opened the valley to scenic carriage and automobile rides in most seasons, particularly south of Military Road. Opening the park to vehicular traffic provided increased public access on both sides of Rock Creek Park. The present road system continues to reflect their original purpose of providing public access to the enjoyment of extraordinary rural scenery. A comparison of a 1918 Olmsted Plan Map, a National Park Service annotated version of that base map prepared in 1941 indicating road conditions in the park, and a modern topography map prepared in 1989, illustrated that the alignment and width of the roads has not changed significantly since 1941. Similarly a comparison of a 1933 map of Rock Creek's facilities reveals that the reservation has retained a high degree of its historic integrity. Although adapted to the automobile, the designed alignment, width and the environmental surroundings of these scenic roads has not substantially changed since the 1920s. According to the 1985 Rock Creek management plan, the road system is 18.79 miles (30.24 km) long and the standard width of roadway is 20 feet (6.1 m). A major non-historic addition to the trail system of the park was the paving of bicycle routes in the 1960s and 1970s.
In addition, the roads serve as connectors to some of Washington's architecture on both sides of Rock Creek Park. For example, the Tiger Bridge can be seen from the Piney Branch Parkway, which is walking distance to Klingle Road and a connector for Mount Pleasant and the adjacent neighborhoods of Crestwood and Rock Creek East. The Bridge appears as a solid arch. This Sixteenth Street Bridge was built in two stages between 1907 and 1910 and was the first parabolic arch bridge built in the United States. The topside of the bridge on Sixteenth Street incorporates simple neoclassical balusters and dramatic tigers, sculptured by noted animalier Alexander P. Proctor, which flank each end of the bridge and lend the bridge its popular name, "Tiger Bridge."
Klingle Road remains listed as an arterial roadway for vehicular traffic on the District of Columbia's Functional Classification Map and is a part of DC's permanent system of highways. Klingle Road remains a right-of-way on the federal-aid system and has not been officially or administratively closed.
Closure and ensuing dispute
A section of the roadway was barricaded in 1990 after erosion severely damaged a 0.75 miles (1.21 km) section. Because the road had been used by up to 3,200 cars a day, a campaign was launched to repair and reopen the road. But a competing campaign, led by the Sierra Club of DC, advocated for replacing the road with a bicycle, hiking, or bridle path.
The repair-and-rebuild group persuaded the DC government to commission a feasibility study by the Berger Group, and engineering consultancy. Published in August 1999, the study ruled out no options, and so did not end the dispute.
In 2003, Mayor Anthony Williams expressed opposition to the demands that the road be rebuilt, but was overruled by the Council of the District, which in 2003 passed a line item in the District budget bill requiring that Klingle Road "be re-opened to the public for motor vehicle traffic." The construction schedule called for the road to be re-opened to motorized traffic in 2007.
An environmental impact study was performed in order to apply for federal funding for the construction. Repeated efforts at this environmental impact study were returned by the federal government to the District for rewriting and changes. In 2008, District Mayor Adrian Fenty attempted to bypass the environmental impact statement by providing full local funding of the automobile road. But Councilmember Mary Cheh, Ward 3, succeeded in replacing this appropriation with a provision calling for the road to "remain closed to motorized vehicular traffic," and the right-of-way employed instead for a non-motorized use trail. Councilmember Jim Graham, Ward 1, attempted to restore funding for the automobile road, but his amendment was rejected by the District Council by a 10 to 3 vote.
After two decades of dispute, the road was replaced with a trail for hikers and bicyclists. A permit to begin restoration of the creek bed, retaining walls, and water permeable trail was granted in Oct. 2014. 
Leading up to this, a 2011 Environmental Assessment resulted in a finding of "No Significant Impact" . This Assessment identified, as the "preferred option", a 10-foot-wide permeable-surface multi-use trail, full stream channel and bank stabilization for Klingle Creek, a multi-use trail connecting this trail to the existing Rock Creek trail, and pole or bollard lighting of the trail to facilitate nighttime use.
On February 28, 2011, the Federal Highway Administration accepted this finding. But the assessment was challenged in Federal Court with a November 1, 2011 lawsuit demanding that the District and Federal governments "refrain from any further planning, acquisition of right-of-way, financing, contracting, or construction of the Klingle Trail Project". On February 1, 2012, the defendants submitted a motion  to have the court dismiss this suit. On August 9, 2012, the U.S. District Court did indeed dismiss the suit, "for lack of subject-matter jurisdiction".
"Klingle Trail Completion" is a $3 million line item in the FY2013-2018 District Capital Improvements budget. Programming $1.5 million in FY2014, and $1.5 million in FY2015, the recreational trail may finally be completed in 2016, 25 years after the closing of Klingle Road due to stormwater damage. Work is scheduled to begin in late 2014 or early 2015. Preliminary work on the Trail began in July, 2015. 
On June 24, 2017, the Klingle Valley Trail was opened to the public.
- "Klingle Valley Trail Project".
- Schaffer, Ron (5 October 1990). "Blinking Banished". The Washington Post.
- District of Columbia Department of Transportation (2001). "The Klingle Road Feasibility Study."
- District of Columbia. Executive Office of the Mayor (2003). "Klingle Road Update." 2003-01-31.
- District of Columbia City Council (2003). "Klingle Road Restoration Act of 2003." Section 2401 of Fiscal Year 2004 Budget Support Act of 2003 (Act A15-0106).
- DDOT (2005). "Klingle Road EIS."
- Wiener, Elizabeth (2008-05-07). "Council panel reopens Klingle Road decision" (PDF). Northwest Current.
- District of Columbia City Council (2008). "Klingle Road Sustainable Development Amendment Act of 2008." Sec. 6016 of Fiscal Year 2009 Budget Support Act of 2008 (Act A17-0419).
- Thoms, Ian (2008-05-14). "Council votes not to reopen Klingle" (PDF). Northwest Current.
- Wiener, Elizabeth (2009-10-07). "Agency readies study of Klingle Road trail" (PDF). Northwest Current.
- Finding of No Significant Impact for Klingle Valley Trail  Accessed 2012-08-11.
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- Federal Motion to Dismiss  Accessed 2012-08-11.
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- Project Update January 2014
- After years of debate, work starts at Klingle Valley Trail