Fluctuations in alongshore wind stress τ calculated from Fleet Numerical Oceanography Center geostrophic winds along the west coast of North America are relatively energetic at alongshore wave numbers |l| ≤ 1.1 × 10−3 cpkm and frequencies 0.025 < ω < 0.5 cpd, and they effectively drive a coastal sea level (ζ) response within this (l, ω) band. Equatorward propagation (l < 0) dominates the winter τ fluctuations for ω < 0.35 cpd, and poleward propagation (l > 0) dominates the summer τ fluctuations for ω < 0.1 cpd. In contrast, poleward propagation strongly dominates the ζ fluctuations in both seasons, but more so in summer. The largest coherence between ζ and τ is observed in that part of (l, ω) space where τ is most energetic: i.e., for 0 ≤ l ≤ 1.1 × 10−3 cpkm in summer and −1.1 × 10−3 ≤ l ≤ 0 cpkm in winter. Results are compared with predictions from theoretical models for wind‐driven coastally trapped waves. The observed transfer functions show evidence for near‐resonant ζ response in both seasons, with the largest gain found along a single ridge of approximately constant poleward phase speed, along which the response is approximately in phase with τ. This behavior is consistent with a response dominated by one coastally trapped wave mode governed by a forced, first‐order wave equation with a linear friction term. The maximum gain tends to decrease along this ridge with increasing l and ω in summer, and at least with increasing ω in winter, during which we could not resolve the l dependence. This observed decrease in maximum gain is not predicted by a single wave equation. The contribution of higher wave modes to the total ζ response may explain a part of this observed decrease.