One of the factors that is supposed to be responsible for exceptional properties in polymer nanocomposites is the inter-phase. The interphase is a region surrounding each nanoparticle where the polymer chains are somehow influenced by the presence of the inorganic surface nearby. It is postulated that due to the high surface area of the nanoparticles that even with a relatively small thickness of interphase around the particle, an appreciable amount of the nanocomposite is in fact this modified interphase material. Despite decades of indirect evidence and speculation about the interphase, there is very little direct evidence, visualization, or detailed measurements of its properties. In this paper we create a strongly coupled system between the surface of a silicon wafer and covalently attached low-T-g elastomer molecules via silane coupling and thiol-ene click chemistry. Then, using advanced scanning probe microscopy techniques coupled with detailed finite element modeling, we determine the true extent of the interphase for this system and measure its mechanical stiffness. We find an interphase of 40 nm in extent, composed of a region of tightly bound rubber with thickness less than 10 nm and shear modulus greater than 250 MPa, and one of loosely bound rubber with thickness around 30 nm and shear modulus around 7 MPa, as compared to the neat polymer shear modulus of 0.3 MPa.