We have analyzedRXTEPCA observations of the pulsed emission fromSGR&hthinsp;1900+14during September 1996, June–October 1998, and early 1999. Using these measurements and results reported elsewhere, we construct a period history of this source for 2.5 years. We find significant deviations from a steady spin-down trend during quiescence and the burst active interval. BATSE observations of the burst emission are presented and correlations between the burst activity and spin-down rate ofSGR&hthinsp;1900+14are discussed. We find an 80 day interval during the summer of 1998 when the average spin-down rate is larger than the rate elsewhere by a factor ∼2.3. This enhanced spin-down may be the result of a discontinuous spin-down event or “braking glitch” at the time of the giant flare on 27 August 1998. ©2000 American Institute of Physics.