This document summarizes recent achievements of the RHIC spin program and their impact on our understanding of the nucleons spin structure, i.e. the individual parton (quark and gluon) contributions to the helicity structure of the nucleon and to und
erstand the origin of the transverse spin phenomena. Open questions are identified and a suite of future measurements with polarized beams at RHIC to address them is laid out. Machine and detector requirements and upgrades are briefly discussed.
