1855History
Several tribes in the region were relocated onto the Yakama Indian Reservation following the 1855 signing of a treaty with the federal government.
1858Military
However, the Yakima War lingered until 1858, with Chief Kamiakin fighting on until the Battle of Four Lakes in 1858.
1870Government
Under the leadership of mayor William Bright "Billy" Cloud (1870–1959), Sunnyside initiated a project to pave its dirt streets on June 5, 1917.
1893Government
The modern settlement of Sunnyside was founded by Walter Granger in 1893.
1901History
By the end of 1901, the population had doubled, finally exceeding 300 people.
1902Government
On September 16, 1902, residents voted 42–1 to incorporate as the town of Sunnyside.
1911Architecture
The original public library, a Carnegie Library, was built in 1911.
1926Economy
Lloyd Miller in 1926.
1927Architecture
Erected in 1927, it is a two-story structure with an adjacent gymnasium attached to the east wing of the building.
1928History
In 1928, female teachers were not allowed to marry.
1948History
In 1948, Sunnyside became the first city in the state to adopt a council–manager system of government.
1964Architecture
It was replaced in 1964 with the current library building.
1979History
Sunnyside was named an All-America City in 1979.
1989History
== Attractions and events ==
=== Lighted Farm Implement Parade ===
First held in 1989, the 'Lighted Farm Implement Parade has been called "the NW's premier lighted parade".
2000History
=== 2000 census ===
As of the 2000 census, there were 13,905 people, 3,827 households, and 3,000 families residing in the city.
2006History
The 2006 edition of the event had more than 70 parade entrants.
2010History
=== 2010 census ===
As of the 2010 census, there were 15,858 people, 4,332 households, and 3,428 families residing in the city.
2012History
The Dairy Fair Store was shut down in 2012.
2015Education
Sunnyside High School was named a School of Distinction in 2015 and 2016.
2020History
The site contained "1 bank, 11 stores, 3 hotels, 1 newspaper [the Sunnyside Sun, still publishing in 2020], 2 blacksmith shops, 2 livery barns, 3 churches, and a large and growi...