THE TOPOGRAPHY and GEOLOGY of SOUTHERN FLORIDA 
SAMUEL SANFORD. 
INTRODUCTION. 
The term Southern Florida is here made to include, for convenience 
of description, that portion of the mainland with its bordering islands 
or keys that lies south of a roughly northeast-southeast line extending 
from the north line of Palm Beach County on the east coast past the 
south end of Lake Okeechobee to the mouth of San Carlos Bay on the 
west coast. The piece of mainland thus arbitrarily cut off has an ex¬ 
treme length, north and south, of 140 miles, and a greatest width, east 
and west, of 120 miles. Its area is about 7,300 square miles, of which 
6,000 square miles are swamp or land so low lying as to be covered 
with water during the rainy season, June to October, or unusually high 
spring tides. The total number of the keys is unknown, but their area 
is here estimated at 300 square miles. 
Growing coral reefs extend along the Florida coast for over 200 
miles and are found nowhere else in the continental limits of the United 
States. Because of the reefs and the teeming marine life of the sur¬ 
rounding waters, Southern Florida has attracted attention for over 
fifty years and has been visited by a number of eminent men who have 
described and discussed the main features of the chain of keys and the 
southeast shore of the mainland. Owing to the difficulties of getting 
about in this region and its comparative remoteness and inaccessibility 
before the building of the Florida East Coast Railway, these visitors 
confined there observations largely to the reef, the shore line of the 
keys and the edge of the mainland in the vicinity of Biscayne Bay. 
While acting as geologist of the Key West Extension of the Flor¬ 
ida East Coast Railway in 1907 and 1908, the writer had an opportunity 
to study in detail some features of the topography and geology that 
were not so evident in former years as they are today. Since the last 
important contributions to the geology of the region, the paper by A. 
Agassiz 1 on the elevated reef, and that by Griswold 2 on the southern 
Everglades the railroad has been completed from Palm Beach to Miami, 
1 Agassiz, Alexander. The Elevated Reef of Florida, Mus. Com. Zool. Bull, 
xxviii, No. 2, 1896, pp. 29-51. 
2 Griswold, Leon S. Notes on the Geology of Southern Florida. Mus. Com. 
Zool. Bull, xxviii, No. 2. 1896, pp. 52-59. 
