  We present a novel formulation of the IP-Glasma initial state model in 3+1D
in which the 2+1D boost invariant IP-Glasma is generalized through JIMWLK
rapidity evolution of the pre-collision Wilson lines \cite{Schenke:2016ksl}. In
order to consistently accommodate a non-boost-invariant system, the initial
conditions are generalized to 3+1D. By breaking boost invariance, the 3+1D
model no longer trivially satisfies Gauss' law at the initial time, and we now
enforce it locally. We compare the time evolution of the chromo-electric and
chromo-magnetic fields as well as the transverse and longitudinal pressures in
the 3+1D case with the boost invariant result.
