  TRAPPIST-1 hosts seven Earth-sized planets transiting an M8 star. We observed
mid-transit times of each of the inner two planets with the Astrophysical
Research Consortium (ARC) 3.5 m Telescope at Apache Point Observatory (APO) to
help constrain the planet masses with transit timing variations, and we outline
a procedure for analyzing transit observations of late-M stars with APO. The
transit times of TRAPPIST-1 b and c are $\mathrm{BJD}_{\mathrm{TDB}} =
2457580.87634^{+0.00034}_{-0.00034}$ and $2457558.89477^{+0.00080}_{-0.00085}$,
respectively, which will help constrain the planet masses.
