Vesto Slipher and the First Galaxy Redshifts
  Priority in the discovery of the velocity-distance relationship may be shifting from Edwin Hubble to Georges Lemaitre, but any reassessment of credit must also consider the contributions of Vesto Slipher. Not only were his spiral galaxy redshifts a necessary component in all of the original velocity-distance plots, but it was the quest to explain these unprecedentedly large Doppler velocities that pointed the way to a new physical interpretation. 
Laird A. Thompson
physics.hist-ph astro-ph.CO