We present high resolution photoelectron energy spectra from multiphoton ionization (MPI) of Ar subject to laser pulses with wavelength of 400 nm, pulse duration of 35 fs, and maximum intensity of 5×10¹³ W/cm². Ionizations into Ar⁺ ²P_3/2 and ²P_1/2 channels are observed and distinct resonance structures are found in both ionization channels. The intensity dependence of the resonance structures is explained in terms of the mechanism of Freeman resonance, i.e., transient resonances of alternating current (AC) Stark-shifted Rydberg states at specific intensities within the laser pulse.