  We present the results of a study on the properties and evolution of massive
(M_* > 10^11 M_0) galaxies at z~0.4 - 2 utilising Keck spectroscopy,
near-Infrared Palomar imaging, and Hubble, Chandra, and Spitzer data covering
fields targeted by the DEEP2 galaxy spectroscopic survey. Our sample is K band
selected based on wide-area NIR imaging from the Palomar Observatory Wide-Field
Infrared Survey, which covers 1.53 deg^2 to K_s,vega~20.5. Our major findings
include: (i) statistically the mass and number densities of M_* > 10^11 M_0
galaxies show little evolution between z = 0 - 1, and from z ~ 0 - 2 for M_* >
10^11.5 M_0 galaxies. (ii) Using Hubble ACS imaging, we find that M_* > 10^11
selected galaxies show a nearly constant elliptical fraction of ~70-90% at all
redshifts. The remaining objects are peculiars possibly undergoing mergers at z
> 0.8, while spirals dominate the remainder at lower redshifts. (iii) We find
that only a fraction (~60%) of massive galaxies with M_* > 10^11 M_0 are on the
red-sequence at z~1.4, while nearly 100% evolve onto it by z~0.4. (iv) By
utilising Spitzer MIPS imaging and [OII] line fluxes we argue that M_* >
10^11.5 galaxies have a steeply declining star formation rate density ~(1+z)^6.
By examining the contribution of star formation to the evolution of the mass
function, as well as the merger history through the CAS parameters, we
determine that M_* >10^11 M_0 galaxies undergo on average 0.9^+0.7_-0.5 major
mergers at 0.4 < z < 1.4. (v) A high (5%) fraction of all M_* > 10^11 M_0
galaxies are X-ray emitters. Roughly half of these are morphologically
distorted ellipticals or peculiars. We compare our results with the Millennium
simulation, finding that the number and mass densities of M_* > 10^11.5 M_0
galaxies are under predicted by a factor of > 100.
