If you tire of Broadway [1] and the beach is too cold and wet, make your way to the Seaside Historical Museum (570 Necanicum Dr., 503/738-7065, 10 a.m.–4 p.m. Mon.–Sat., noon–3 p.m. Sun. late Mar.–Oct., noon–3 p.m. Mon.–Sat., noon–3 p.m. Sun. Nov.–late Mar.; $3 adults, $2 seniors, $1 students), housed in a classic seaside cottage six blocks north of Broadway, where Clatsop artifacts and exhibits on early tourism in Seaside [2] will impart more of a sense of history than anything else in town.
Links:
[1] http://www.moon.com/destinations/oregon/north-coast/seaside/sights/the-promenade-and-broadway
[2] http://www.moon.com/destinations/oregon/north-coast/seaside