A good source for general information about Maple Syrup is Maple Syrup in Wikipedia.
Below is a description of the process that we have used in the past to make maple syrup. Unfortunately, the warming of our climate has made further production of maple syrup not feasible at our farm.
Maple Creek Farm is the furthest southern commercial producer of maple syrup in the US, and the only one located in North Carolina. Our "sugar bush" consists of two stands, each with more than 200 Sugar Maple trees, located on the north and east facing slopes of two mountainsides. The stands are high on the slopes between 3,100 and 3,900 feet in elevation. We currently have about 500 taps in about 400 trees. Over four miles of tubing and piping carries the maple sap from the trees down the mountain to the "sugar shack" in the valley between the mountains. The sap all moves by gravity, which along with rocks, we have an abundance of on the farm (note the slope in the picture below).
In a good year, one tap will generally produce around one quart of maple syrup.
We use a traditional wood-fired evaporator which came from New Hampshire, which is housed in a new "sugar shack" which we recently completed.
While maple syrup producers up north are still warming thier feet by the fire (and digging out from under the snow), we are boiling syrup. This far south, the sap starts to flow in early January. And when the sap flows, we start cooking, because the sap will spoil quickly if it is not processed.
The evaporator uses a continuous flow process, where sap trickles in at one end of the evaporator, and flows through a serpentine (syrupentine?) path to the other end of the evaporator, where it is "drawn off" as syrup when the sugar concentration is correct.
From when the evaporator is started up, the first "draw" of syrup comes after about 16 hours of boiling.
Thereafter, we draw off about two gallons of syrup every three hours.
After filtering, the piping hot maple syrup is immediately filled into glass jars. It doesn't get any purer or fresher than that!