At eye-opening, layer 2/3 (L2/3) of ferret primary visual cortex (V1) exhibits orientation-selective responses, modular (~periodic) patterns of visually-evoked and spontaneous activity, and spatially periodic orientation maps. L4 activity has weaker orientation selectivity (OS) than, and is spatially uncorrelated with, L2/3 responses at eye-opening, suggesting L2/3 may generate modular activity patterns independently of L4 map or activity organization. Here we characterize L4 and L2/3 receptive fields (RFs) and the L4 orientation map at eye-opening. We then model the connectivity by which L4 inputs and L2/3 recurrence can generate selective and modular evoked activity in L2/3, and the development of the RFs and connectivity seen at eye-opening. L4 and L2/3 show strong similarities in their RF ON/OFF subregion arrangements at eye-opening, suggesting L2/3 cells receive afferent L4 inputs with overlapping RFs. While most L4 cells show weak OS, its more selective cells have elongated, single-subregion RFs. Compared to predictions from the ON/OFF subregions, electrophysiological (EP) spike responses have less modulation vs. grating phase (i.e., are more complex-cell like) in both layers, but similar OSs in L4. From this, we infer that the L4 orientation map is locally-correlated while its phase maps are nearly random. We study a model of excitatory (E) L4 units projecting to both E and inhibitory (I) L2/3 units. We show the above results will arise if L4 maps have smoothly varying preferred orientations (POs), with more strongly-selective cells in sparse spatial clusters. Local recurrent excitation makes responses more complex-cell-like in both layers. Strong, anisotropic L2/3 lateral connectivity transforms weakly selective and unstructured L4 input into highly selective, modular activity patterns with periodic orientation maps. Finally, we show that L4 naturally develops the initial biased, elongated RFs and locally-correlated orientation maps when geniculate activity is wave-like and inhibitory plasticity is Hebbian.