PSTA's roots trace back to the early 1900s as the St. Petersburg Municipal Transit System (SPMTS).

The system began with a streetcar line to Gulfport and eight buses to run several routes throughout the St. Pete area.

In 1928, the entire SPMTS system carried 4.2 million customers, marking a major milestone for the agency.

[3][4] Despite the demise of the Gulfport trolley, bus service throughout Pinellas County continued to expand throughout the 1940s, 50s, and 60s.

By the 1980s, the two agencies formed a cooperative agreement, which allowed the expansion of routes throughout Pinellas County.

The agency begins installing electronic fareboxes and completed its central Pinellas operations center, as well as several bus terminals.

In 1990, PSTA obtained its first express route, previously operated by Hillsborough Area Regional Transit (HART).

A year later, PSTA and HART introduced an intersystem Passport to allow customers to use each other's systems for a single monthly fare.

In 2005, PSTA relocated all of its operations to a single, unified facility in northern St. Petersburg - near Ulmerton Rd and Roosevelt Blvd.

This began with a Memorandum of Understanding (MOU) between the agency, the Tampa Bay Area Regional Transit Authority (TBARTA), the Florida Department of Transportation (FDOT), and the Pinellas County Metropolitan Planning Organization (MPO) to conduct an Alternatives Analysis of transit corridors in Pinellas County.

[7] In 2012, the agency launched the North County Connector flex-route van service, allowing customers in areas of northern Pinellas to have access to transit service - including those in neighborhoods by which regular transit buses have difficulty accessing or where a traditional fixed bus route would have lower ridership projections.

[8] In 2017, PSTA began Direct Connect, which allows customers to summon a ride via taxi or ride share to connect to or from a designated stop or bus terminal "PSTA Brings Together Uber and Taxi to get People on the Bus".

In 2018, a partnership between PSTA, HART, Pasco County Public Transportation, and transit agencies in Hernando, Manatee, and Sarasota counties began working on a regional fare collection system called Flamingo Fares Tampa Bay.

This system would allow customers to use either a smartphone app or a smart card to tap a reader device and pay for their transit fares in a seamless, contactless manner.

[9] The same year, PSTA announced that it would partner with Transit App to help provide real-time bus arrival predictions and eventually other features to customers via the use of smartphones.

[10] The agency also introduced its first two battery electric buses - produced by BYD, and revamped Route 300X to serve Tampa International Airport on most trips.

[14] Despite delays in the project - partly due to the COVID-19 pandemic, the SunRunner opened to customers on October 21, 2022 to great fanfare.

[15] On January 10th, 2025, PSTA opened the new 150 1st Ave North station, featuring glass artwork created by Catherine Woods.

A new program was launched on January 10th, called "Sunrunner After Dark"; which extended the full service hours until midnight on Friday and Saturday nights.

Effective January 2, 2024, PSTA would stop accepting the old "GO Cards", in favor of contactless payment via Flamingo Fares.

The CAT traverses Central Ave between Downtown St. Pete's Pier District and Grand Central Station, while the SBT traverses Gulf Blvd between Clearwater Beach and St. Pete Beach (the latter also serves Downtown Clearwater via the Memorial Causeway Bridge).

The sub-network used cutaway vans to access areas of northern Pinellas County that would be otherwise inaccessible to standard transit buses.

Since 2009, PSTA has been planning some form of Bus Rapid Transit service to better serve customers along higher-ridership corridors.

In the mid 2010s, concrete plans were presented for the county's first BRT route utilizing the aforementioned corridors.

Buses continue to run on their full schedule until midnight on Friday and Saturday nights due to a program called "Sunrunner after dark", launched in January 2025.