  We report measurements of the charge-separated $W^{+(-)} \to e^{+(-)} +
\nu_e(\bar{\nu}_e)$ and $Z/\gamma^* \to e^+e^-$ production cross sections at
mid-rapidity in proton-proton collisions at $\sqrt{s}$ = 500 GeV. These results
are based on 13.2 pb$^{-1}$ of data recorded in 2009 by the STAR detector at
RHIC. Production cross sections for W bosons that decay via the $e \nu$ channel
were measured to be $\sigma(pp \to W^+ X) \cdot BR(W^+ \to e^+ \nu_e)$ = 117.3
\pm 5.9(stat) \pm 6.2(syst) \pm 15.2(lumi) pb, and $\sigma(pp \to W^- X) \cdot
BR(W^- \to e^- \bar{\nu}_e)$ = 43.3 \pm 4.6(stat) \pm 3.4(syst) \pm 5.6(lumi)
pb. For $Z/\gamma^*$ production, $\sigma(pp \to Z/\gamma^* X) \cdot
BR(Z/\gamma^* \to e^+ e^-)$ = 7.7 \pm 2.1(stat) $^{+0.5}_{-0.9}$(syst) \pm
1.0(lumi) pb for di-lepton invariant masses $m_{e^+e^-}$ between 70 and 110
GeV/$c^2$. First measurements of the W cross section ratio, $\sigma(pp \to W^+
X) / \sigma(pp \to W^- X)$, at $\sqrt{s}$ = 500 GeV are also reported.
Theoretical predictions, calculated using recent parton distribution functions,
are found to agree with the measured cross sections.
