42 plus one Dog. Of which 33 were American Soldiers and 9 were Civilian Guides and Servants . 29 of the Group went to the Pacific while 12 carried the samples of the first year's exploration back to St Louis and Washington and one Sargent Charles Floyd died , the only member of the expedition to die in it's travels, of a rupture appendix near what is to day Sioux City Iowa.
The number includes Sacajawea' infant son.