  Detailed models of the solar cycle require information about the starting
time and rise time as well as the shape and amplitude of the cycle. However,
none of these models includes a discussion of the variations in the length of
the cycle, which has been known to vary from $\sim$7 to 17 years. The focus of
our study was to investigate whether this range was associated with a secular
pattern in the length of the sunspot cycle. To provide a basis for the analysis
of the long-term behavior of the Sun, we analyzed archival data of sunspot
numbers from 1700 - 2005 and sunspot areas from 1874 - 2005. The independent
techniques of power spectrum analysis and phase dispersion minimization were
used to confirm the $\sim$11-year Schwabe Cycle, and to illustrate the large
range in the length of this cycle. Long-term cycles were identified in archival
data from 1610 -- 2000 using median trace analyses of the length of the cycle,
and from power spectrum analyses of the (O-C) residuals of the dates of sunspot
minima and maxima. The median trace analysis suggested that the cycle length
had a period of 183 - 243 years, while the more precise power spectrum analysis
identified a period of 188 $\pm$ 38 years. We found that the 188-year cycle was
consistent with the variation of sunspot numbers and seems to be related to the
Schwabe Cycle. We found a correlation between the times of historic minima and
the length of the sunspot cycle such that the length of the cycle was usually
highest when the actual number of sunspots was lowest. The cycle length was
growing during the Maunder Minimum when there were almost no sunspots visible
on the Sun. This information can now be used to improve the accuracy of the
current solar cycle models, to better predict the starting time of a given
cycle.
