It lasted from 1914-1917, mirroring other movements in avant-garde artwork such as Cubism.
Imagism was a revolt against the more widely used victorian-era style poetry. The idea was to use only the words required to complete an image, and cut out all the extraenous fluff.
Some of the more famous poets involved in this movement were:
H.D (short for Hilda Doolittle)
For such a short movement, imagism influenced a great many 20th century poems, most noticeably, free-verse and beat poets.