[4] Protests began locally within the state of Hawaii on October 7, 2014 but went global within weeks of the April 2, 2015 arrest of 31 people who had blockaded the roadway to keep construction crews off the summit.

The project was expected to be completed by 2024, nearly simultaneously with the 39-meter Extremely Large Telescope being built in Chile; however, on December 2, 2015, the Supreme Court of Hawaii invalidated the TMT's building permits.

The TMT corporation then removed all construction equipment and vehicles from Mauna Kea, and re-applied for a new permit, meant to respect the Supreme Court's ruling.

He persuaded then-governor John A. Burns, to bulldoze a dirt road to the summit where he built a small telescope on Puʻu Poliʻahu, a cinder cone peak.

Testing also determined Mauna Kea to be superb for nighttime viewing due to many factors including the thin air, constant trade winds and being surrounded by sea.

[15] Although polls, some of them highly criticized,[23] indicate that a majority of Hawaii residents support the Thirty Meter Telescope,[24] opposition to the project and other observatories has existed since 1964.

Native Hawaiian cultural practitioners kānaka ʻōiwi believed the entire site was sacred and that developing the mountain, even for science, would spoil the area.

Once access was opened up by the roadway to the summit, skiers began using it for recreation and objected when the road was closed as a precaution against vandalism when the telescopes were being built.

[27] The Audubon Society objected to further development on Mauna Kea over concerns to habitat of the endangered palila, an endemic species to only specific parts of this mountain.

A 2006 proposal for the Outrigger Telescopes to become extensions of the Keck Observatory was canceled after a judges determination that a full environmental impact statement must be prepared before any further development of the site.

The group raised several other concerns such as environmental over native insects, the question of Ceded lands and an audit report, critical of the mountain's management.

[48][49] Beginning in late March 2015 demonstrators halted construction crews near the visitors center, again by blocking access of the road to the summit of the mountain.

Daniel Meisenzahl, a spokesman for the University of Hawaii, stated that the 5 tractors trailers of equipment that were moved up the mountain the day before had alerted protesters that began organizing the demonstrations.

Kamahana Kealoha of the group Sacred Mauna Kea stated that over 100 demonstrators had traveled up to the summit to camp overnight, to be joined by more protesters in the early morning to blockade crews.

A number of celebrity activists of Native Hawaiian descent, both local and national, began campaigning over social media, including Game of Thrones star Jason Momoa who urged Dwayne Johnson (The Rock) to join the protests with him on top of Mauna Kea.

[56] In response to the growing protests the TMT Corporation's division of Hawaii Community Affairs launched an internet microsite, updating content regularly.

[70] It was announced on August 9, that astronomers at other Mauna Kea observatories would return to work after halting for many weeks in response to the gathering protesters and activists.

However, a former systems specialist for one of the facilities claimed it was wrong to blame the demonstrators stating: "They chose to close down for fear of protesters who are unarmed and nonviolent.

"[71] On 19 December, Governor David Ige announced at a press conference that he was reopening the access road and withdrawing law enforcement from the mountain [1].

[72] Shortly after sunrise on July 13, 2019, the Royal Order of Kamehameha, along with Mauna Kea protectors began the process of designating Puʻuhuluhulu as a puʻuhonua which, historically, has served as a space of protection during contentious times.

The Puʻuhonua o Puʻuhuluhulu boundaries were secured through ceremony and the approval of the Royal Order of Kamehameha, establishing a site of protection, sanctuary and refuge for Mauna Kea protectors.

[77] Due to the altitude and harsh weather conditions at Puuhonua o Puuhuluhulu, the Mauna Medics treat illnesses such as hypothermia, sunburn, and dehydration.

[78] “Presley Keʻalaanuhea Ah Mook Sang, a Hawaiian language instructor at the University of Hawaii at Mānoa, said she first came up with the idea to start a community-led school or “teach-in” after witnessing the crowd swell in that first week from hundreds of protesters to thousands”.

[78] On the Mauna Kea access road in front of what is now known as the kupuna (elders) tent there is daily protocol at 8am, 12noon and 5:30pm, in which protectors and visitors are able to learn and participate in Hawaiian cultural practices such as oli (chant), hula, and hoʻokupu (offerings).

In July 2023, a new state appointed oversight board, which includes Native Hawaiian community representatives and cultural practitioners, began a five-year transition to assume management over Mauna Kea and its telescope sites, which may be a path forward.

Concern was raised over the content of the email, with the wording of "a horde of native Hawaiians" to describe the protesters considered to be problematic and potentially racist.

[96] Scientists have taken to Twitter and other social media platforms to voice their support publicly for the protest using #ScientistsforMaunaKea, in which they highlight their field and why they feel that the TMT is not needed on the mountain.

[citation needed] Native Hawaiian academics from various fields have also voiced their opposition to the telescope and participated in the protests themselves, such as Oceanographer Rosie Alegado.

[98][99][100] On July 20, 2019 an online petition titled "A Call to Divest Canada's Research Funding for the Thirty Meter Telescope on Mauna Kea" has been posted on Change.org.

Others, such as Leonardo DiCaprio, Bruno Mars, Emilia Clarke, Nathalie Emmanuel, Rosario Dawson, Jill Wagner, Jai Courtney, Kelly Slater and Madison Bumgarner have used social media to promote the cause.