  If $L^x$ is the total occupation local time of $d$-dimensional super-Brownian
motion, $X$, for $d=2$ and $d=3$, we construct a random measure $\mathcal{L}$,
called the boundary local time measure, as a rescaling of $L^x e^{-\lambda L^x}
dx$ as $\lambda\to \infty$, thus confirming a conjecture of \cite{MP17} and
further show that the support of $\mathcal{L}$ equals the topological boundary
of the range of $X$, $\partial\mathcal{R}$. This latter result uses a second
construction of a boundary local time $\widetilde{\mathcal{L}}$ given in terms
of exit measures and we prove that $\widetilde{\mathcal{L}}=c\mathcal{L}$ a.s.
for some constant $c>0$. We derive reasonably explicit first and second moment
measures for $\mathcal{L}$ in terms of negative dimensional Bessel processes
and use it with the energy method to give a more direct proof of the lower
bound of the Hausdorff dimension of $\partial\mathcal{R}$ in \cite{HMP18}. The
construction requires a refinement of the $L^2$ upper bounds in \cite{MP17} and
\cite{HMP18} to exact $L^2$ asymptotics. The methods also refine the left tail
bounds for $L^x$ in \cite{MP17} to exact asymptotics. We conjecture that the
Minkowski content of $\partial\mathcal{R}$ is equal to the total mass of the
boundary local time $\mathcal{L}$ up to some constant.
