The Story of the Florida Railroads by George W. Penttengill, Jr: reprint from the Southeast Chapter of the Railway and Locomotive Historical Society.
Still available at the better train shows of the Southeast.

Through the Heart of the South: The Seaboard Airline Railroad Story by Robert Wayne Johnson.Boston Mills Press.

    The early players:

The line from Jacksonville to Alligator Town (Lake City) was built between 1857 and 1860 by the Florida Atlantic & Gulf Central RR.
The section from Tallahassee to Alligator Town was built by the Pensacola & Georgia RR between 1856 and 1861. The construction started in Tallahassee at the connection with the Pensacola & Georgia RR owned Tallahassee RR. It connected in Alligator Town with the Florida Atlantic & Gulf Central RR in 1861.
The Pensacola & Georgia RR also built the Tallahassee-Quincy portion in 1861.
In 1870, the P&G RR was sold and renamed Jacksonville Pensacola & Mobile RR. The JP&M RR built the track from Quincy to River Junction in 1872.

    Mergers: formation of the Seaboard Air Line.

In 1870, the Jacksonville Pensacola & Mobile RR started leasing the Florida Atlantic & Gulf Central RR that had been sold and renamed the Florida Central RR. The 2 lines were merged in 1879. The railroad became part of the Florida Railway & Navigation Co, which eventually was integrated into the Seaboard Air Line in 1903.

Baldwin: Florida Atlantic & Gulf Central RR connected in 1859 with the Florida RR.
Live Oak: The Florida Law that forbade the building of Railroads across the border with Georgia stood until the Civil War. The Confederate Government decided to build a line from Lawton (Dupont) Ga on the Atlantic & Gulf RR to Live Oak Fl on the Pensacola & Georgia RR. The P&G RR owned the line to the border. The line opened in 1865 after the Civil War had ended. Three other lines were connected to the main line in Live Oak: The Live Oak Perry & Gulf RR; The Live Oak & Gulf RR and The Suwannee & San Pedro RR (Three well-documented sites written by Donald R. Hensley).
Drifton: the P&G RR built A branch line to Monticello in 1861.
Tallahassee: the Tallahassee RR built a line to Port Leon in 1836. After a hurricane destroyed Port Leon in 1843, the railroad end point became St Marks.

The Florida Georgia & Western Ry was organized to build a line from Bainbridge to Tampa in 1891. A little bit of the line was built in 1891 from Tallahassee toward the east on what probably is Tram Rd today. The FG&W Ry was reorganized in 1895 as the Tallahassee Southeastern Ry to build a line from Tallahassee to Gainesville. The line was completed in 1899 to Wacissa and graded past the Aucilla River. The Tallahassee Perry & Southeastern Ry (Seaboard Air Line) acquired the line in 1905, and completed the line from Wacissa to Covington 11 miles in 1906 and to Waylonzo 8 miles in 1907. It was operated as a logging line. The towns of Covington and Waylonzo have now disappeared from current maps.

The Augusta Tallahassee & Gulf RR built in 1888 a line from Carabelle to the Ocklokonee River and became the Carrabelle Tallahassee & Georgia RR. It completed the line to Tallahassee in 1893. Georgia Florida & Alabama absorbed the line in 1906.

The Georgia Florida & Alabama was organized in 1895 as the Georgia Pine Ry Co. Track was built in 1898 between Bainbridge and Arlington. The name GF&A was adopted in 1901. Track was completed to Cuthbert in 1902. The line from Bainbridge to Tallahassee was built in 1902 as well. A branch from Havana to Quincy was completed in 1906. In 1910, the line reached Richland where it connected to the Seaboard Air Line. In 1928, the Seaboard Air Line leased the GF&A for 99 years.

The Pelham & Havana was chartered in the late 1800s. The line was only from Cairo to Havana where it connected with the GF&A line to Tallahasse and with the branch to Quincy. There is not a trace of it left today. The railraod was named by the users the Poor & Hungry.