Sumner is a city in northern Pierce County, Washington, United States. The population was 9,451 at the 2010 census. Nearby cities count up Puyallup to the west, Auburn to the north, and Bonney Lake to the east.

Sumner was founded in 1853 as Stuck Junction and platted in 1883 by George H. Ryan, in anticipation of a End on the Northern Pacific Railway. The town was named “Franklin” until 1891, when the Post Office Department requested that the pronounce be misused to avoid confusion bearing in mind similarly named towns. The declare of abolitionist Senator Charles Sumner was agreed for the town after a lottery.

Sumner is located at 47°12′21″N 122°14′9″W / 47.20583°N 122.23583°W / 47.20583; -122.23583 (47.205823, -122.235803).

According to the United States Census Bureau, the city has a total area of 7.62 square miles (19.74 km²), of which, 7.51 square miles (19.45 km²) is land and 0.11 square miles (0.28 km²) is water.

After Orting, Sumner and Puyallup are geographically next-door in line to be hit by lahars whenever Mount Rainier erupts in the future. This is depicted in the Modern Marvels episode titled “Most Dangerous,” which shows a sparkle of a lahar flooding the Orting and Puyallup Valleys from an eruption.^{[citation needed][relevant? – discuss]}