We show that an
-Brownian
Gibbsian line ensemble is completely characterized by the finite-dimensional
marginals of its lowest-indexed curve for a large class of interaction Hamiltonians
. A particular
consequence of our result is that the KPZ line ensemble is the unique line ensemble that satisfies the
-Brownian Gibbs
property with
and whose lowest-indexed curve is equal to the Cole–Hopf solution to the narrow
wedge KPZ equation.