Gerard Peter Kuiper (1905-1973), in 1951, proposed the exsistence of this large flattened distribution of objections in relation with his theory of the orgin of the solar system.  Kenneth Edgeworth (1880-1972) had, independently, made similar proposals in 1943 and 1949.  Whether the belt extends thinly as far as the Oort Cloud is not known.  The Gravitational distrubances by Neptune of objects in the belt are thought to be the origin of most short-period comets we see and know of today.  The first Kuiper belt object was discovered in 1992, although the orbit, icy composition, and diminutive size of Pluto appear to quality this body, traditionally considered a planet, as a giant Kuiper belt object!