  The North American Nanohertz Observatory for Gravitational Waves (NANOGrav)
has observed dozens of millisecond pulsars for over a decade. We have accrued a
large collection of dispersion measure (DM) measurements sensitive to the total
electron content between Earth and the pulsars at each observation. All lines
of sight cross through the solar wind which produces correlated DM fluctuations
in all pulsars. We develop and apply techniques for extracting the imprint of
the solar wind from the full collection of DM measurements in the recently
released NANOGrav 11-yr data set. We filter out long time scale DM fluctuations
attributable to structure in the interstellar medium and carry out a
simultaneous analysis of all pulsars in our sample that can differentiate the
correlated signature of the wind from signals unique to individual lines of
sight. When treating the solar wind as spherically symmetric and constant in
time, we find the electron number density at 1 A.U. to be $7.9\pm0.2$
cm$^{-3}$. Our data shows little evidence of long-term variation in the density
of the wind. We argue that our techniques paired with a high cadence, low radio
frequency observing campaign of near-ecliptic pulsars would be capable of
mapping out large-scale latitudinal structure in the wind.
