Question: What date did the Stonehenge visitors center open?
About the article "Stonehenge", section "Setting and access".

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American horror writer H. P. Lovecraft, an enthusiast for New England megalith stone sites, is known to have visited Mystery Hill sometime between 1928 and the 1930s.
Mystery Hill is popularly attributed as inspiration for Lovecraft's story "The Dunwich Horror".
Scholars, however, place Lovecraft's visit too late to have inspired the 1929 story.
The site was featured on an episode of the American History Channel TV series "Secrets of the Ancient World" which aired on January 14, 2002, and in which Boston University archaeology professor Curtis Runnels refuted the theory that the site was built by Celts in ancient history.
"In Search of...", a 1970s show narrated by Leonard Nimoy, did an episode about the site, titled "Strange Visitors".
It was referred to as "Mystery Hill".
In the "Weird or What?"
TV series hosted by William Shatner, the "Human Popsicle" episode covered America's Stonehenge and a variety of explanations as to its origin.
In the pseudo-documentary TV series "America Unearthed", hosted by Scott Wolter, the episode "Stonehenge in America" dealt with the possible connections of the site to Stonehenge in England and the Phoenician culture.
It is also mentioned briefly in the X-Files episode "Die Hand Die Verletzt". 
 America's Stonehenge, located just east of the center of North Salem  
John Frederick Smerdon Stone (1891?
– 1957) was a British archaeologist, most famous for his work in and around Wiltshire, especially at Stonehenge and the Woodhenge area.
In 1947, Dr Stone excavated the first ever trench across the Stonehenge cursus, at a site near the Fargo Plantation a little north west of the stone circle.
This permitted its dating for the first time and Dr Stone was able to establish its prehistoric date and that it had been constructed using antler picks in irregular sections.
In the cursus ditch fill, he also found a piece of Welsh stone, incorrectly described as a fragment from the Cosheston Beds of Milford Haven.
Coupled with the finds of bluestone fragments found between the cursus and Stonehenge, Dr Stone hypothesised that an earlier bluestone monument, predating the megalithic stages of Stonehenge, had stood near the cursus and been subsequently moved and re-erected on its current spot.
In 1950, Dr Stone joined R. J. C. Atkinson and Stuart Piggott in an excavation at Stonehenge itself.
Commissioned by the Society of Antiquaries, their work recovered many cremations and developed the phasing that still dominates much of what is written about Stonehenge. 
By the beginning of the 20th century many of the bluestones were leaning precariously, probably due to the increase in curious visitors clambering on them during the nineteenth century.
Additionally two of the trilithons had fallen over during the modern era.
Three phases of conservation work were undertaken which righted unstable or fallen stones and carefully replaced them in their original positions using information from antiquarian drawings.
The first of the significant excavations at Stonehenge was led by Colonel William Hawley and his assistant Robert Newall after the site had come into state hands in 1918(see Deed of Gift of Stonehenge dated 26 October 1918).
He excavated portions of most of the features at Stonehenge and was the first to establish that it was a multi-phase site.
After the Second World War, the Universal Bond was permitted to re-commence its ceremonies although archaeologists such as Glyn Daniel and Stuart Piggott continued to campaign against what they saw as bogus Druidry throughout the 1950s, 60s and 70s.
In 1950 the Society of Antiquaries commissioned Richard Atkinson, Stuart Piggott and John FS Stone to carry out further excavations.
They recovered many cremations and developed the phasing that still dominates much of what is written about Stonehenge.
More recent minor excavations have been held to mitigate the effects of electrical cables, sewage pipes, and footpaths.
In 2005, excavations as part of the Stonehenge Riverside Project uncovered the remains of what may have been a village for workers or festival-goers near Stonehenge.
The site, next to Durrington Walls, about two miles from Stonehenge is also the location of a large timber monument.
The floors of several homes have since been discovered, as well as tools, animal bones, arrowheads and several more monuments.
The head of the project - Mike Parker Pearson - speculates that Stonehenge and Durrington Walls may have been connected by the nearby River Avon, as both monuments have Avenues which lead to the river.
He further considers it possible that the area around Stonehenge may have been the burial area for people living around Durrington Walls, and would have made up a 'Domain of the dead', whilst the village was in the 'Domain of the living'.
According to historical researcher Michelle Wilson, "What we have been looking at is a 20th Century landscape, which is reminiscent of what Stonehenge MIGHT have been like thousands of years ago.
It has been created by the heritage industry and is NOT the creation of prehistoric people.
What we saw at the Millennium is less than 50 years old."
  The only astronomically-aligned, full-scale, "exact" replica of (a pristine) Stonehenge in natural stone (granite) is at Esperance in Western Australia (esperancestonehenge.com.au).
Some of the blocks weigh more than fifty tonnes and the replica cost over A$250 000 to build  The Maryhill Stonehenge: A full-size concrete replica of Stonehenge, as it would have been originally built, saw construction commence and was originally dedicated on July 4, 1918.
Built in Maryhill, Washington by Sam Hill, it was the first monument in the United States to honor the dead of World War I (specifically, soldiers from Klickitat County, Washington who had died in the still on-going war).
The altar stone is placed to be aligned with sunrise on the Summer Solstice.
Hill, a Quaker pacifist, was mistakenly informed that the original Stonehenge had been used as a sacrificial site, and thus constructed the replica as a reminder that "humanity is still being sacrificed to the god of war."
The monument was originally located in the center of Maryhill, which later burned down leaving only the Stonehenge replica.
A second formal dedication of the monument took place upon its completion on May 30, 1929.
Sam Hill, who died in 1931, lived long enough to see his Stonehenge completed.
A Stonehenge replica is located on the campus of the University of Texas of the Permian Basin in Odessa in Ector County, Texas.
About twenty stone blocks, similar in size, shape, and appearance to the ancient Stonehenge in southwestern England, were unveiled in the summer of 2004.
Stonehenge Aotearoa in the Wairarapa region of New Zealand is a modern adaptation aligned with the astronomy seen from the Antipodes, it was built by the Phoenix Astronomical Society from wood and sprayed concrete.
Foamhenge is a full-size, astronomically-aligned Stonehenge made out of foam near Natural Bridge, Virginia.
"It is the only American Stonehenge that really is an exact replica of the time-worn original."
"I went to great pains to shape each 'stone' to its original shape."
British Foamhenge; a full size, correctly aligned replica made from carpet tubes and polystyrene was constructed for a UK TV show entitled "Stonehenge Live" broadcast in June 2005.
The positions of each stone were accurately plotted using RTK GPS, which has centimetric accuracy.
The replica quickly became known as "Foamhenge".
It was removed soon after filming, and the 'stones' remain in storage (January 2006).
Missouri S&T has a half-scale replica built from solid granite located on campus.
A full-scale replica in sandstone was commenced in the rural township of Buckland in Tasmania in the first years of the 21st century (www.flickr.com/photos/ron-alenka/284418892/)but demolished by order of the municipal authorities.
In keeping with the original Stonehenge, it did not have the necessary planning approval from the local council...