Statistics for occurrence #1 of “St. Marks” in chapter 2 of Col. J. J. Dickison, Confederate Military History, a library of Confederate States Military History: Volume 11.2, Florida:

... posts, the keys to the Gulf, were held by the enemy. There were a few cannon mounted at St. Augustine, at Fort Clinch on Amelia island, at the mouth of St. John's river, at Fernandina, Cedar Keys, St. Marks , Apalachicola and Tallahassee; but there were only two guns at each of the gulf points, and St. Augustine had but eleven. At this time (May) it was estimated that Florida had 70000 men in the field...
Max. Freq. Min. Freq.
Entity Corpus Doc Corpus Doc  
St. Marks (Florida, United States) 13 0 1 0 0 user votes
St. Marks (Florida, United States) 0 0 0 0 0 user votes
St. Marks (Georgia, United States) 0 0 0 0 0 user votes
St. Marks (Indiana, United States) 0 0 0 0 0 user votes

† This entity has been selected by the automated classifier as the most likely match in this context. It may or may not be the correct match.