Space Florida, the state's aerospace economic development agency, wants to build a commercial spaceport next to Kennedy Space Center. Local business and government officials are all for the chosen site, seeing it as a way to boost the future of the Space Coast now that America's shuttle program has ended.

But the past sometimes reaches out to trip the future.

The property along the Volusia-Brevard county line where Space Florida wants to build its spaceport turns out to be already occupied. It contains the ruins of an 18th century English plantation, complete with slave villages, a sugar factory and a rum distillery. National Park Service officials have declared it "one of the most significant properties in North America."

"This site, what they're proposing, they'll be right smack on it," said Roz Foster, a local historian who runs the North Brevard Heritage Foundation in Titusville. When she informed Space Florida of what was there, though, "they were surprised that it existed."

That dismayed Foster because the ruins had been fully explored and documented by archaeologists five years ago. "They should have known," she said.

The Elliott Plantation, built in the late 1760s, covers about 2,500 acres and "contains the remains of a complete sugar works factory … two overseers' homes and two slave villages," according to a National Park Service archaeology report filed in March. "This is one of the most significant and well-preserved African-American landscapes known, and is unique in its quality of preservation."

The plantation's owner, William Elliott, lived in England and depended on his Scottish overseer, John Ross, to run the place and send him reports, said National Park Service archaeologist Margo Schwadron. The letters they exchanged, including diagrams of the plantation, have all been the subject of research in London, she said.

Ross acquired more than 80 slaves from Georgia to dig canals draining wetlands on the property so they could grow sugar, rice and indigo. The slaves also ran the sugar factory and distillery.

Ross fell in love with a slave named Bella, Schwadron said. He arranged for her to be freed, then married her. They had two daughters he sent to Scotland to be educated.

The plantation operated until 1779, when Spanish privateers raided it and carted off all the plunder they could carry, as well as burning a 60-acre sugar cane field that had been ready for harvest.

The remaining slaves were sold to a plantation in St. Augustine, and the owner abandoned all the buildings, leaving behind "miles of slave-built canals, irrigation ditches, old fields, gardens, roads, paths … and cleared areas where indigo and sugar production were undertaken on a very large scale," the park service report states.

"The place has been pretty much untouched since then," Schwadron said. While any wood rotted away, the 2008-09 excavation work uncovered intact stonework and bricks made of coral, not to mention shards of ceramic dishes and other artifacts.

The plantation's sugar factory is particularly important, said Dot Moore, the archaeologist who first located the ruins and has since worked on excavating and documenting what's there.

"We think it was the earliest one in North America, so it has a unique historic significance," she said. It was also the southernmost English plantation in the country.

The Elliott Plantation site is so significant, in fact, that the park service report says that because of the proposal for the spaceport, it should be nominated as a National Historic Landmark to protect it.

Space Florida spokeswoman Tina Lange said considerations about the fate of that site "will very much be a part of the environmental impact statement process going forward. Sensitivity to sites of cultural heritage is listed as a specific category to be considered … and will impact the final determination."

Space Florida has been working since 2009 on setting up a commercial spaceport operation on the state's Atlantic coast. Last fall, after what the agency called an "exhaustive search" of the state's east coast, it formally requested that NASA turn over 150 acres just north of Kennedy Space Center named "Shiloh" after an abandoned citrus town nearby.

Center director Bob Cabana approved the launch of an environmental impact study of the Shiloh property, which could take a year or more.

The Shiloh site is designed to appeal to a specific customer, SpaceX of California, which is also considering locations in Texas and Puerto Rico. The site is far enough from existing NASA launch complexes to avoid conflict with their operations, yet close enough to "provide critical cross pollination opportunities between government and commercial launch activities to the benefit of both," Space Florida says on its website.

However, the Shiloh site has already drawn opposition from environmental groups such as Audubon of Florida because of concerns about its impact on the Merritt Island National Wildlife Refuge, a 140,000-acre sanctuary that overlaps NASA's property. The revelation that there's also a major archaeological site there "is not a little problem," environmental activist Clay Henderson said.

Craig Pittman can be reached at craig@tampabay.com