Essential HTN. Essential HTN is the cause of most hypertension. We can treat it though we don't truly know the cause. A very small percentage of hypertension are known as secondary htn, have known causes such a renal artery stenosis, pheocromocytoma and other rare disorders. These are rare. I have personally had two cases in twelve years of active practice... More important that the cause is aggressive treatment.
It is a long history. William harvey (1578–1657) first described the circulation of blood in his book "de motu cordis", 1733 stephen hales published the first measurement of bp, descriptions of it as a disease came from thomas young in 1808 and richard bright in 1836 among others. In 1896, the invention of the cuff-based sphygmomanometer by scipione riva-rocci brought HTN as a clinical entity.