Strom was the capital of the ancient human nation/empire of Arathor.
Having unified all the tribes of humanity under one banner, King Thoradin constructed a great fortress in the area now known as the Arathi Highlands. The nomadic tribes congregated on the site, providing humanity with a strong defense against the forest trolls of Zul'Aman.
As such, Strom is often considered the "father nation" of the humans on Azeroth, and its security allowed the gathered tribes to prosper in the surrounding regions. Farms were established on the low lying lands of Arathi and soon the humans influence reached out east and south. The establishment of Strom was key to allowing humans to secure themselves as a dominant race. Its positioning meant that both the dwarves to the south and the elves to the north were within reach, allowing trade to instigate a flourishing society, only hampered by occasional troll raids from the eastern fringes in the Hinterlands.
Following the fracturing of Arathor into smaller kingdoms, a few warriors remained behind to defend the capital, which was renamed Stromgarde, but it fell into disrepair and is now no more than a shattered shell of its former self.