  The advent of space-based missions like $Kepler$ has revolutionized the study
of solar-type stars, particularly through the measurement and modeling of their
resonant modes of oscillation. Here we analyze a sample of 66 $Kepler$
main-sequence stars showing solar-like oscillations as part of the $Kepler$
seismic LEGACY project. We use $Kepler$ short-cadence data, of which each star
has at least 12 months, to create frequency power spectra optimized for
asteroseismology. For each star we identify its modes of oscillation and
extract parameters such as frequency, amplitude, and line width using a
Bayesian Markov chain Monte Carlo `peak-bagging' approach. We report the
extracted mode parameters for all 66 stars, as well as derived quantities such
as frequency difference ratios, the large and small separations $\Delta\nu$ and
$\delta\nu_{02}$; the behavior of line widths with frequency and line widths at
$\nu_{\rm max}$ with $T_{\rm eff}$, for which we derive parametrizations; and
behavior of mode visibilities. These average properties can be applied in
future peak-bagging exercises to better constrain the parameters of the stellar
oscillation spectra. The frequencies and frequency ratios can tightly constrain
the fundamental parameters of these solar-type stars, and mode line widths and
amplitudes can test models of mode damping and excitation.
