The theory to obtain orientation information from polar-ized Raman spectra has been described in extensive detail elsewhere. The key step is to determine the respective most probable orientation distribution functions, N mp (θ ), for the the Amide I A(0, 0) tensor of each polymorph. The method of finding N mp (θ ) is described in the section Basic Approach to Determine the Most Probable Orientation Distribution Function of the SI. Briefly, for systems such as fibrils with uniaxial symmetry, N mp (θ ) can be estimated with reasonable accuracy by experimentally measuring two order parameters called ⟨P 2 ⟩ and ⟨P 4 ⟩. As discussed in detail in the SI, these order parameters can be determined from the intensity ratios R 1 = I ZX /I ZZ and R 2 = I XZ /I XX for the Amide I A(0, 0) mode (see Table and S2 and Figures ). Figure -c shows N mp (θ ) for the Amide I A(0, 0) tensors. The distributions are normalized such that multiplying N mp (θ ) by sin θ yields the preferred orientation distribution of the tensors. As shown in Figure -g, preferred orientation distributions of the Amide I A(0, 0) tensors for all the polymorphs are bimodal. The maximum probability for the distributions corresponding to the Amide I A(0, 0) tensors occur at ca. ±10°and ±15°for amylin 20-29 polymorphs 1 and 2, respectively, and ±11°for Aβ 25-35 fibrils (Table ). These values indicate that the β-strands of the polymorphs are oriented approximately perpendicularly to the fibril long axis, which is the hallmark of the cross-β architecture observed in amyloids. The smaller peaks in the C--O bond angle distributions that occur at 90°can be attributed to local disordering of the cross-β structure or because of misalignment of the fibrils filaments in the coffee rings that we prepared. Based on the relative intensities of the peaks, disordering and misalignment accounts for roughly 19% for both amylin 20-29 polymorphs and 33% for Aβ 25-35 fibrils of the total probability for the C--O bond angle distributions.