Answer: L = Low Pressure; H = High pressure
Atmospheric pressure is measured with instruments on the ground called "barometers", and these measurements are collected and analyzed through many locations in the U.S. As seen in the map, on the north parts of Florida, it is seen that there is "High Pressure", since it has an "H" to represent the pressure there. On the South parts of Florida, probably where Naples and Miami are, there is "Low Pressure", since it is represented with an "L". These two letters are very important in weather maps because it tells how the weather is on a certain place, since atmospheric pressure is what causes the different types of weather.
Step-by-step explanation:
Hope this helps =)