The Sunnyslope Church began its life as a Church of the Brethren congregation. Amos B. Peters, an elder in the Church of the Brethren, accepted an assignment from the Great Northern Railroad to promote settlement of the Wenatchee valley by Brethren who were tired of cold winters in North Dakota. Several families followed his lead and moved to the Wenatchee Valley, where they found a living desert with snow-covered mountains. Mountain waters ultimately became the source of water that would make the desert bloom and become amazing fruit orchards.
The church formally organized in 1902, holding its first worship service on May 10, 1903. An active Sunday School program began in August of 1903. Originally called the Wenatchee Church of the Brethren, it was the first Church of the Brethren in the valley. The name was changed to Sunnyslope Church of the Brethren in 1937.
In the 1980’s, the congregation took official action to acknowledge and honor its members with UCC ties by affiliating with the United Church of Christ.