  The White Mountain Polarimeter (WMPol) is a dedicated ground-based microwave
telescope and receiver system for observing polarization of the Cosmic
Microwave Background. WMPol is located at an altitude of 3880 meters on a
plateau in the White Mountains of Eastern California, USA, at the Barcroft
Facility of the University of California White Mountain Research Station.
Presented here is a description of the instrument and the data collected during
April through October 2004. We set an upper limit on $E$-mode polarization of
14 $\mu\mathrm{K}$ (95% confidence limit) in the multipole range
$170<\ell<240$. This result was obtained with 422 hours of observations of a 3
$\mathrm{deg}^2$ sky area about the North Celestial Pole, using a 42 GHz
polarimeter. This upper limit is consistent with $EE$ polarization predicted
from a standard $\Lambda$-CDM concordance model.
