Mars Global Surveyor (MGS) Magnetometer (MAG) data provide constraints on magnetic morphology at Mars, including the relative importance of the solar wind and of crustal magnetic sources. We analyze MAG data to characterize the upstream interplanetary magnetic field (IMF) and confirm trends in the magnetic field expected from the solar wind interaction with a planetary atmosphere, including increases at the shock and magnetic pile-up boundary (MPB), postshock turbulence, and field line draping around the Martian obstacle. Crustal magnetic sources locally modify the solar wind interaction, adding variability to the Martian magnetic environment that depends on planetary rotation. We identify trends in the vector magnetic field with respect to altitude, solar zenith angle, and planetary location. Crustal sources influence the magnetic field to different altitudes above different regions, and the influence of the strongest source extends to 1300--1400 km. The draped IMF partially controls the field topology above crustal sources, and crustal magnetic field lines reconnect to this field in a systematic fashion that depends upon Mars' geography, IMF strength, and IMF orientation.