  We have found that the ability of long thin rods to jam into a solid-like
state in response to a local perturbation depends upon both the particle aspect
ratio and the container size. The dynamic phase diagram in this parameter space
reveals a broad transition region separating granular stick-slip and solid-like
behavior. In this transition region the pile displays both solid and stick-slip
behavior. We measure the force on a small object pulled through the pile, and
find the fluctuation spectra to have power law tails with an exponent
characteristic of the region. The exponent varies from $\beta=-2$ in the
stick-slip region to $\beta=-1$ in the solid region. These values reflect the
different origins -- granular rearrangements vs. dry friction -- of the
fluctuations. Finally, the packing fraction shows only a slight dependence on
container size, but depends on aspect ratio in a manner predicted by a mean
field theory and implies an aspect-ratio independent contact number of $<c > =
5.25 \pm 0.03$.
