Resonance enhanced second harmonic spectra of the chromophore 4-aminobenzophenone (4ABP) were recorded at different solid/liquid interfaces. The solid substrates were hydrophilic silica and the solvents varied in size, shape and dielectric properties. Solvatochromic comparisons between SHG spectra of adsorbed 4ABP and excitation spectra of 4ABP in bulk solution reveal how solvent-substrate interactions and solvent structure alter interfacial solvent polarity from bulk solution limits. Not surprisingly, weakly associating systems consisting of polar substrates and nonpolar solvents are more polar than bulk solution, although there exist subtle, solvent-dependent differences in the strength of interfacial solvent-solute interactions. These differences are attributed to a solvent's ability to pack against a rigid wall. Measurements of solute orientation at weakly associating interfaces supports a model in which the solute experiences multiple interactions with the substrate and adopts an orientation that is deflected significantly from the surface normal. Solvent polarity across strongly associating interfaces depends sensitively on solvent structure. Interfaces formed between hydrophilic silica substrates and n-alcohol solvents are significantly less polar than bulk solution, but branched alcohols create regions of enhanced local polarity. These effects are discussed in terms of the substrate's ability to induce long-range structure in the adjacent solvent through hydrogen-bonding interactions. Again, orientation measurements support the interfacial polarity results. In strongly associating systems, interfacial solutes adopt an orientation that is consistent with simulation predictions of alkyl chain tilt angles at extended solid surfaces.