The San Jacinto Monument is listed on Obeliskth century  The question of it being an obelisk was raised in  and got no replies while this question also from  got one negative reply  I would say there is for now no actual consensus  However if San Jacinto was ruled to not be an obelisk the next tallest could be the Juche Tower in Pyongyang North Korea which is about  ft taller than the Washington Monument  It has four sides but then again you could argue the top is still too ornate for it to be an obelisk