Following the Civil War, the county commission established the county seat on donated in the central part of the county. Bartow, the county seat, was named after Francis S. Bartow, a confederate Colonel from Georgia who was the first confederate officer to die in battle during the first battle of the Civil War. Colonel Bartow was buried in Savannah, GA with military honors, and promoted posthumously to the rank of brigadier general. Fort Blount , as Bartow was then known, in a move to honor one of the first fallen heroes of the Confederacy, was one of several towns and counties in the South that changed their name to Bartow. The first courthouse built in Bartow was constructed in 1867. It was replaced twice, in 1884 and in 1908. As the third courthouse to stand on the site, the present structure houses the Polk County Historical Museum and Genealogical Library.
The discovery of phosphate rock in the Peace River, near Fort Meade, Florida in 1881, initiated the mining of the world's largest deposit of phosphate rock, known as the Bone Valley Deposit. This deposit, which encompasses approximately 500,000 acres (2000 km²) in Polk, Hillsborough, Hardee, and Manatee Counties, provides approximately 75% of the nation's phosphate supply and about 25% of the world supply. Approximately 200,000 acres (800 km²) or 15.3% of Polk County have been mined for phosphate rock. Polk continued to lead the state in 1998, with 14.7 million tons of phosphate rock mined. However, four straight years of low prices and weak demand for phosphate fertilizer led to a loss in sales in 2002. The industry's impact on the Polk County economy will continue to decline in the 21st Century as phosphate mining moves south into Hardee and Desoto Counties.
Chemical manufacturing plants located in Polk County are used to convert the insoluble phosphate rock into soluble products, such as diammonium phosphate and monoammonium phosphate, which are used in fertilizers and other products. There are numerous, other industries located in Polk County which support and rely on the phosphate mining industry. In October 2004, IMC Global, Inc. and Cargill Crop Nutrition merged into the Mosaic Co. This merger created the world's second largest fertilizer manufacturer with annual sales estimated at $4.5 billion. Mosaic employs more than 3,000 workers in Polk County at five active mines, Four Corners, Fort Green, Kingsford, South Fort Meade and Hookers Prairie; and two fertilizer plants, Ridgewood and New Wales (reputed to be the largest fertilizer plant in the world).
Polk County has the 2nd largest amount of farmland in the state with an estimated 626,634 acres (2536 km²) in 2002. Polk remains the sixth most productive agricultural county in Florida . The $878 million citrus industry employs approximately 8,000 people in Polk County . Polk ranked first in the state for total citrus picked for the 2003-04 season with an estimated total of 42.2 million boxes harvested. Polk also ranked first in the state in the amount of commercial citrus groves with approximately 95,050 acres (385 km²), 2004 estimate. In addition to citrus, Polk was ranked third in the state in 2004, in number of beef cattle with an estimated 105,000 head of beef and dairy cattle, according to the Florida Agricultural Statistics Service. Total receipts from the sale of crops and livestock in Polk County rose to $284.8 million in 2002 based upon a report released by the Bureau of Economic Analysis at the U.S. Department of Commerce.
Tourism is a strong economic force in Polk County and dates back to the dedication of Bok Tower Gardens in 1929 by President Calvin Coolidge. In the mid-1930s, the late Dick Pope, Sr. established the world famous Cypress Gardens in Winter Haven , Florida's first theme attraction. (Polk County is also home of a roadside attraction: Spook Hill.) Today, millions of people visit Polk County each year to enjoy these two attractions as well as Fantasy of Flight, the Sun ‘N Fun Fly-In, and many more. Polk County is also located within a one hour drive of the Walt Disney World resort area, Universal Studios, SeaWorld, and Busch Gardens. In addition to these attractions, Polk is the spring training headquarters for the Detroit Tigers (Lakeland). The county had an estimated total of 11,500 hotel, motel, rental condominium units and vacation rentals in 2004.
In recent years, Polk County has gained notoriety as a preferred venue for recreational and competitive sports on all levels. In 2001, the county hosted 140 sporting events that pumped in excess of $84 million into the local economy. This is in addition to $72 million generated by the Spring Training operation of the Detroit Tigers. Polk County Sports Marketing, the sports marketing arm of the Board of County Commissioners, was honored as Florida's “Sports Commission of the Year” by the Florida Sports Foundation for its success in promoting the county as a sports destination.
Today, phosphate mining, agriculture and tourism still play vital roles in the local economy. However, the county has successfully expanded and diversified its economic base in recent years. The primary mission of the Central Florida Development Council (CFDC) since its formation in 1985 by the Board of County Commissioners, has been to improve the standard of living for the citizens of Polk County by diversifying the economy through job creation in all industries. The CFDC has successfully worked with other industries to help them expand and relocate to Polk County . Polk County's central location within the large Florida marketplace has attracted numerous manufacturers and distribution centers in recent years.
Construction is a pillar of economic strength for Polk County with a record of 5,900 total permits issued for single family homes in 2004. This is an increase of approximately 68.7% over a total of 3,498 building permits issued in 2003 for single family homes. The total number of homes sold in 2004, was 5,300, an increase of 7.8% over a total of 4,918 homes sold in 2001.
Polk County is the sole county in the Lakeland Metropolitan Statistical Area.
There were 187,233 households, of which 29.00% had children under the age of 18 living with them, 54.40% were married couples living together, 12.00% had a female householder with no husband present, and 29.30% were non-families. 24.10% of all households were made up of individuals, and 11.10% have someone living alone who was 65 years of age or older. The average household size was 2.52 and the average family size was 2.96.
In the county the population was spread out, with 24.40% under the age of 18, 8.30% from 18 to 24, 26.40% from 25 to 44, 22.50% from 45 to 64, and 18.30% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 96.30 males. For every 100 females age 18 and over, there were 93.10 males.
The median income for a household in the county was $36,036, and the median income for a family was $41,442. Males had a median income of $31,396, versus $22,406 for females. The per capita income for the county was $18,302. 12.90% of the population and 9.40% of families were below the poverty line. Out of the total population, 19.10% were under the age of 18 and 8.10% were 65 or older.
As of July 1, 2005, the U.S. Census Bureau estimated the county had 542,912 residents, making it the ninth most populous county in Florida.
What in fact existed was a non-partisan Florida political culture, best described by V.O. Key, Jr., in the classic, "Southern Politics," (Knopf, 1950) as "every man for himself." Coalitions gravitated around special economic interests. Polk County's role was magnified by the presence of two big-money industries, phosphate and citrus. Park Trammell, Spessard Holland, and Lawton Chiles each served in the legislature, as governor, as a U.S. senator. The county's political style, when not satisfying local industry, was small-town economic populist: building roads, schools, and parks, but wary of social liberalism.
A watershed moment in Polk County politics came with the election of Andy Ireland to Congress. Ireland was the first modern Polk politician without local roots, an outsider culturally and personally from a wealthy Ohio family and with an upper-class education at Andover and Yale. He moved to Winter Haven as a bank executive. His election reflected the growing factor of in-migrants, who were slowly weakening the deeply rooted local populist traditions. It was Ireland who set off a wave of party switching by moving from the Democratic party to the Republican party in 1984, taking career advantage of Ronald Reagan's popularity and grassroots distrust of national Democrats as the perceived party of racial integration and sexual license. Within a few years, there was a rapid switch of parties, both by many prominent political figures in the county and by the white public at large. By the early 1990s, Polk County had become one of the most reliably Republican counties in state. Native son Lawton Chiles continued to win U.S. Senate races from 1970 to 1982, and in the 90s was elected governor twice ironically without Polk's support.