Strong or low-barrier hydrogen bonds have often been proposed in proteins to explain enzyme catalysis and proton-transfer reactions. So far H-1 chemical shifts and scalar couplings have been used as the main NMR spectroscopic signatures for strong H-bonds. In this work, we report simultaneous measurements of N-15 and H-1 chemical shifts and N-H bond lengths by solid-state NMR in N-15-labeled 1,8-bis(dimethylamino)naphthalene (DMAN), which contains a well-known strong NHN H-bond. We complexed DMAN with three different counteranions to examine the effects of the chemical environment on the H-bond lengths and chemical shifts. All three DMAN compounds exhibit significantly elongated N-H distances compared to the covalent bond length, and the H-1(N) chemical shifts are larger than similar to 17 ppm, consistent with strong NHN H-bonds in the DMAN cation. However, the N-15 and H-1 chemical shifts and the precise N-H distances differ among the three compounds, and the N-15 chemical shifts show opposite dependences on the proton localization from the general trend in organic compounds, indicating the significant effects of the counteranions on the electronic structure of the H-bond. These data provide useful NMR benchmarks for strong H-bonds and caution against the sole reliance on chemical shifts for identifying strong H-bonds in proteins since neighboring side chains can exert influences on chemical shifts similar to those of the bulky organic anions in DMAN. Instead, N-H bond lengths should be measured, in conjunction with chemical shifts, as a more fundamental parameter of H-bond strength.