 It served the entire state of Oregon.Despite Oregon's dramatic growth in the second half of the 20th century, particularly in the Willamette Valley (Portland and Eugene), 503 remained Oregon's sole area code for 48 years, making Oregon one of the largest states with just one area code.However, by the early 1990s, 503 was on the brink of exhaustion due to the proliferation of cell phones and pagers, particularly in the Portland area.