A History of the Phosphate Industry in Central Florida

By Joe Marzo

Central Florida sits atop one of the richest phosphate deposits on Earth — a band of land stretching across Polk, Hillsborough, Hardee, and Manatee counties known as Bone Valley. For roughly 140 years this region has supplied a quiet but essential ingredient of modern life: the phosphorus that fertilizes the world's crops and that goes into animal feed, toothpaste, food preservatives, and a range of industrial products. The story of the industry is also the story of the land it transformed, the workers who dug it, and the environmental reckoning that followed.

Geological Origins

Florida owes its phosphate to the sea. Millions of years ago much of the peninsula lay submerged under shallow marine waters, and the slow rain of marine organisms, bones, and chemically rich sediments accumulated in vast beds. The Pliocene-age Bone Valley Formation, weathered from the older Miocene Hawthorn Formation, eventually became one of the most economically accessible phosphate deposits in the world. The name “Bone Valley” comes from the spectacular fossils that emerged alongside the ore — gomphotheres (four-tusked elephant relatives), giant sloths, primeval crabs, and tens of thousands of other specimens that paleontologists from the Florida Museum of Natural History have catalogued from the mines. As one curator has noted, many of these fossils would never have come to light without the industry that exposed them.

Discovery, 1881–1888

The industry traces to a chance discovery during a routine federal survey. In the winter of 1881, Captain J. Francis LeBaron, a civil engineer with the U.S. Army Corps of Engineers, was surveying the Peace River south of Fort Meade for a proposed canal to link the headwaters of the St. Johns River with Charlotte Harbor. He noticed unusual pebbles in the riverbed and identified them as phosphate. The find sat dormant for several years.

Hard-rock phosphate mining actually began first, in 1883 near Hawthorne in Alachua County. The central Florida boom started a few years later. In 1886, John C. Jones and Captain W. R. McKee confirmed additional deposits along the Peace River and quickly organized a company to begin extraction. Mining of “river pebble” phosphate along the Peace River got underway in 1888, and the Peace River Phosphate Company began commercial operations in the winter of 1889, shipping ore by barge to Punta Gorda and from there to Europe.

The Boom Years, 1890–1914

The discovery set off one of Florida's first great industrial rushes. Within a decade of LeBaron's finding, more than 200 companies were mining phosphate in central Florida, and the price of an acre of Peace River land had risen from $1.25 to roughly $300. Prospectors fanned out west of the Peace River and found something even better than river pebble: thick beds of “land pebble” phosphate covered by only twenty to fifty feet of sand and clay. Stripping that overburden was far cheaper than dredging river bottoms or chasing the harder rock of north Florida, and Bone Valley quickly became the industry's center of gravity.

The town of Mulberry crystallized around this trade. A railroad originally built for the lumber and turpentine industries ran through the heart of the new mining district, and a depot near a large mulberry tree became the natural transshipment point for several surrounding mines. The town incorporated in 1901, and for the next seventy years it served as the unofficial capital of the Bone Valley phosphate industry. Early mining was crude — picks, shovels, and human muscle in pits thirty feet deep — but the geology was generous enough that even simple methods paid.

Rail networks expanded to serve the mines. Narrow-gauge lines connected Arcadia, Hull, and the Peace River load-outs to the Florida Southern Railway, which in turn fed export terminals at Punta Gorda, Port Tampa, Seddon Island, Boca Grande, and Rockport. By the 1890s, Florida had displaced South Carolina as America's leading phosphate producer, and the central Florida district has held that position ever since.

Labor, Race, and the 1919 Strike

The labor history of Bone Valley was harsh. Miners worked twelve-hour shifts in knee-deep slurry under armed guards on horseback, paid roughly two dollars a day, with regular dynamite accidents that maimed or killed coworkers. The workforce was a mix of Black and white laborers in the segregated Jim Crow South, and conditions were brutal enough by the end of World War I to produce a remarkable moment of interracial labor solidarity.

In April 1919, about 3,000 miners, organized through the International Union of Mine, Mill, and Smelter Workers, struck against seventeen Bone Valley mining companies, demanding a minimum wage, an eight-hour day, and safer conditions. The companies brought in strikebreakers from Georgia and cut electricity to Mulberry and nearby Fort Meade. On the evening of August 21, 1919, mine guards for the Prairie Pebble Phosphate Company opened fire on the town. The seven-month strike unfolded during the national “Red Summer” and braided labor conflict with racial violence. It ended on December 3 when most of the phosphate companies agreed to roughly double wages and shorten the workday by at least two hours.

The strike's effects rippled globally. Trade journals described 1919 as a year of uncertain supply and high prices for fertilizer worldwide, and Germany's Secretary of Agriculture reported in 1920 that German farms had received only about 28 percent of the phosphoric acid fertilizer they needed.

Mechanization and Mid-Century Expansion

The 1920s brought the walking dragline — enormous machines, some weighing up to eight million pounds, that could “walk” across the landscape on huge mechanical feet, scraping away overburden and digging out phosphate matrix at scales no shovel crew could match. Draglines increased mining capacity by roughly an order of magnitude and reshaped both the economics and the landscape of Bone Valley, leaving behind the cratered, moonlike terrain that became the region's visual signature.

Foreign investment poured in. In 1920, the British firm Andrew Weir & Co. purchased 30,000 acres in the district, and the industry consolidated into larger, more capital-intensive operations through the interwar period. From 1952 to 1961, and again from 1976 to 1998, uranium was recovered as a byproduct at central Florida phosphate plants — the Bone Valley deposits naturally contain about 100 parts per million uranium, and the district remains North America's largest uranium resource, with an estimated one million tons of recoverable uranium still in the ground.

Until roughly the 1950s, fertilizer manufacturing in central Florida remained relatively small and regionally tailored. The postwar agricultural revolution changed that. Demand for chemical fertilizer surged as American and global farming industrialized, and central Florida's processing plants grew into massive complexes producing phosphoric acid by reacting phosphate rock with sulfuric acid. U.S. phosphate production peaked nationally in 1980 at 54.4 million metric tons, with the central Florida district supplying the lion's share. The United States held the title of world's largest phosphate producer from about 1900 until 2006, when China surpassed it.

The Environmental Reckoning

The same processing chemistry that made the modern fertilizer industry possible also produced its most troublesome waste. For every ton of phosphoric acid manufactured, roughly five tons of byproduct are generated, most notably phosphogypsum — a mildly radioactive solid that, because of its radium content, has been barred from most commercial uses and instead piled into enormous “gypstacks” hundreds of feet tall. Central Florida is now studded with these stacks, each one a long-term liability.

A series of disasters made the costs visible. In 1997, a dam atop a gypsum stack at the Mulberry Phosphates fertilizer plant failed during heavy rains and sent 56 million gallons of acidic wastewater into the North Fork of the Alafia River, killing more than a million fish along the 42-mile path to Tampa Bay; the company declared bankruptcy and shut down. In 2001, after Mulberry Phosphates collapsed, ammonia-laden waste flowed from the abandoned Piney Point stack in Manatee County into Tampa Bay breeding grounds. 2004 brought another spill: Tropical Storm Frances whipped up waves atop a 180-foot gypstack at Mosaic's Riverview plant, breaching the dike and releasing 65 million gallons into Archie Creek and Hillsborough Bay. Piney Point ruptured again in 2011 (about 170 million gallons) and again in 2021, when more than 200 million gallons of polluted process water had to be released into Tampa Bay to prevent a catastrophic collapse.

Reclamation lagged the damage. Mines opened before 1975 had no obligation to restore the land they tore up, and large areas of the upper Peace River basin were left in their post-mining state for decades. Stricter rules followed: the Florida legislature created the Florida Institute of Phosphate Research (now the Florida Industrial and Phosphate Research Institute, housed at Florida Polytechnic University) in 1978, and after July 1, 1996, new mines have required Environmental Resource Permits with substantially tighter standards for wetlands, water quality, and post-mining land use. Restoration projects such as the Upper Peace River / Saddle Creek work have begun to convert legacy mine lands into wildlife habitat and recreation areas, including the Tenoroc Fish Management Area, and the regional Integrated Habitat Network plan now guides reclamation design across the 1.3-million-acre district.

Consolidation and the Modern Industry

The fragmented industry of the early twentieth century — with its hundreds of small operators — has consolidated into a handful of giants. After successive mergers among IMC Global, Cargill's crop nutrition unit, and other firms, The Mosaic Company emerged in 2004 as the dominant central Florida producer and today mines the Bone Valley district essentially on its own.

Mosaic produces roughly 8 million tons of finished phosphate per year in Florida, with the capacity to produce up to 10 million, and reported pumping an average of 34 million gallons of groundwater per day in 2022 to support that production. As older mines in Polk and Hillsborough counties have been depleted, the company has pushed south into Hardee and Manatee counties, drawing sustained controversy over the trade-offs between economic activity, water use, and downstream effects on the Peace River and Charlotte Harbor estuary.

The industry now employs roughly 3,900 people directly in Florida. Port Tampa Bay, the export gateway for the district, moved 3.9 million tons of phosphate in 2021 — down from 8 million tons in 2017, reflecting both shifting global trade patterns and the long, slow maturation of the deposit. China, Morocco, and the United States together account for the bulk of world phosphate output, with central Florida still supplying a meaningful share of global demand for a fertilizer ingredient that has no large-scale substitute.

Legacy

Central Florida's phosphate industry has been, by turns, a frontier rush, a backbone of the global food system, the engine of company towns and labor struggles, the source of some of the state's worst environmental disasters, and the steward of a slowly evolving reclamation regime. The cratered land, the gypstacks on the skyline near Mulberry and Riverview, the cataloged fossils in Gainesville, the shipping terminals at Port Tampa Bay, and the unresolved questions about Piney Point and its successors are all part of the same hundred-and-forty-year story. The geology that drew LeBaron up the Peace River in 1881 still defines a region whose past, present, and future are bound to the rock beneath it.