The city is home to the administrative offices of North Cascades National Park, which lies east of Sedro-Woolley on State Route 20.

[4] Four British bachelors, led by David Batey, homesteaded the area in 1878, the time logjam obstructions were cleared downriver at the site of Mount Vernon.

Cook intended to name his new Pacific Northwest town Bug due to the number of mosquitos present, but his wife protested along with a handful of other local wives.

In 1889, Northern Pacific Railway developer Nelson Bennett began laying track from the town of Fairhaven, 25 miles (40 kilometres) northwest on Bellingham Bay, and real estate developer Norman R. Kelley platted a new town of Sedro on high ground a mile northwest of Cook's site.

The Fairhaven and Southern Railroad arrived in Sedro on Christmas Eve, 1889, in time for Bennett to receive a performance bonus from the towns at both ends, and a month after Washington became the 42nd state in the Union.

[7] Within months, two more railroads crossed the F&S roadbed a half mile north of new Sedro, forming a triangle where 11 trains eventually arrived daily.

Railroad developer Philip A. Woolley moved his family from Elgin, Illinois, to Sedro in December 1899 and bought land around the triangle.

Meanwhile, a fourth town rose nearby when the F&S laid rails on a "wye" that led northeast from Sedro about four and a half miles to coal mines.

The resulting ore soon turned out to be more suitable for coking coal and a town began there named Cokedale.

He was the largest circus elephant in captivity at the time, measuring 10 feet 2 inches (3.10 m) tall and weighing 7.5 short tons (6,800 kg).

Tusko demolished several fences, knocked down telephone poles, and destroyed a Model T. He was chased by local residents for 30 miles (48 km) in the surrounding countryside, and was captured the following morning.

[8] After logging and coal-mining declined, the major employers and industries became the nearby Northern State Hospital (a mental-health facility)[9] and Skagit Steel & Iron Works, which rose from the back room of a local hardware store to become a major supplier of implements and parts for logging and railroad customers.

[16][17] The municipal judge is appointed by the mayor, subject to confirmation of the city council, and operates independently of the other branches of government.

The city maintains a large number of public parks and open spaces such as Hammer Heritage Square in downtown Sedro-Woolley.