A United Nations agency on Sunday named the Alamo and the four Spanish colonial Catholic missions in San Antonio a World Heritage Site, making them the first places in Texas deemed to be of “outstanding cultural or natural importance to the common heritage of humanity”.

The decision capped a nine-year campaign by San Antonio and Texas to have the early 18th-century missions listed alongside world treasures such as Stonehenge, the Taj Mahal and Angkor Wat. The missions are now the 23rd World Heritage Site in the US.

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“The city of San Antonio is delighted with Unesco’s decision today and the recognition that our Spanish colonial missions are of outstanding value to the people of the world,” mayor Ivy Taylor said from Bonn, Germany, where the announcement was made.

Sarah Gould, archivist at the Institute of Texan Cultures, said there were many reasons for the listing of the four missions, which are still used as Catholic churches, and the Alamo, a fortified church, barracks and other buildings that was the scene of the 1836 battle for Texan independence.

“Other than the Alamo, which has had quite a bit of changes to it, the other four are in really wonderful condition,” Gould said, “almost in as good a condition as they were when they were built.”

As well as creating the basis for European settlement of what is now the US southwest, she said the missions were important in the formation of its early economy, for instance by introducing cattle raising.

Casandra Matej, director of San Antonio’s convention and visitors bureau, said the listing would prompt a full scale, international tourism campaign. She estimated it will mean more than 1,000 new jobs for the city’s already robust tourism industry, and a $100m annual boost for the region.

But the designation has not been entirely embraced in Texas, where the phrase “United Nations” provokes suspicion among some. The Texas Republican Party’s official platform includes opposing “granting jurisdiction and sovereignty over Texas’ cultural sites to any international body”.

Matej said there was no way that would happen, and noted that the UN exercised no “sovereignty” over other US World Heritage sites, such as Philadelphia’s Independence Hall or Thomas Jefferson’s Monticello home in Virginia.

“The current management, how everything is managed, will stay the same,” she said. “This is a designation that will draw visitors to our destination, and allow us to share our splendid missions with the world.”