  We have identified 335 galaxy cluster and group candidates spanning 0<z<2,
using a 4.5um selected sample of galaxies in a 7.25 deg^2 region in the
Spitzer/IRAC Shallow Survey. Using full redshift probability distributions for
all galaxies, clusters were identified as 3-dimensional overdensities using a
wavelet algorithm. To date 12 clusters at z>1, and over 60 at z < 0.5 have been
spectroscopically confirmed. The mean I-[3.6] color for cluster galaxies up to
z~1 is well matched by a z_f=3 passively evolving model. At z>1, a wider range
of formation histories is needed, but higher formation redshifts (i.e. z_f \ge
4-5) are favored for most clusters. The cluster autocorrelation function,
measured for the first time out to z=1.5, is found not to have evolved over the
last 10 Gyr, in agreement with the prediction from LCDM. The average mass of
the IRAC Shallow Cluster Survey sample, inferred from its clustering, is ~
10^14 Msun.

Astrophysics