for spectral classification studies and comparisons with model atmospheres. McLean et al. (2003a), hereafter M03, describes the lower resolution part of the survey; spectra from that study are available online.[^2] Here, we investigate the $J$-band using ten times higher spectral resolution than in M03. The $J$-band (defined as 1.15-1.36 $\mu$m in this paper) is important because this region contains four strong lines of neutral potassium (K I) that are both temperature and gravity-sensitive, and which persist throughout the M, L, and T dwarf sequence. In §2 we describe our observations and data reduction procedures. §3 provides a discussion of the rich, spectral morphology. In addition to atomic K I, there are lines of Al I, Fe I, Mn I, Na I and Ti I, and transitions of molecular species such as CrH, FeH, and H$_{2}$O that can provide a unique resource for improving model atmospheres at these low temperatures. We show that the sudden disappearance of the Al I lines critically defines the M-L boundary at these resolutions. Concentrating on the strongly pressure-broadened K I lines, we look for correlations between spectral type and equivalent widths, velocity widths (FWHM), and residual intensity. The relation between molecular line strengths and spectral 