  The physics goals that will be addressed by colliding polarized protons at
the Relativistic Heavy Ion Collider (RHIC) are described. The RHIC spin program
provides a new generation of experiments that will unfold the quark, anti-quark
and gluon contributions to the proton's spin. In addition to these longer term
goals, this paper describes what was learned from the first polarized proton
collisions at $\sqrt{s}$=200 GeV. These collisions took place in a five-week
run during the second year of RHIC operation.
