Membership in the WMO is not limited to sovereign states; it may include territories that maintain their own meteorological services. Membership is open to any of the 45 states and 30 territories attending the 1947 conference in Washington that signed the convention or to any member of the UN with a meteorological service. Any of these automatically becomes a member of the WMO upon ratifying or acceding to the convention. Any other state, territory, or group of territories maintaining its own meteorological services may become eligible for membership upon approval of two-thirds of the WMO membership. As of 1 July 2001, the WMO had 185 members.