United and uniting churches

[2][3] Historically, unions of Protestant churches were enforced by the state, usually in order to have a stricter control over the religious sphere of its people, but also for other organizational reasons.

[5][6][7][8] In the developing world, this model has been attractive in countries where Protestants are a small minority of the population; by pooling resources and endorsing cross-attendance between denominations, churches can serve a wider geographical area.

In the developed world, since the mid-20th century, and the rise of secularism worldwide, mainline Protestantism has shrunk, reducing the viability of many individual denominations maintaining parallel administrative structures.

[9][10][11][12] Among others, Reformed (Calvinist), Anglican, and Lutheran churches have merged, often creating large nationwide denominations.

The COCU disbanded formally in 2002 but moved into the Churches Uniting in Christ movement.

Glass window in the town church of Wiesloch ( Stadtkirche Wiesloch ) with Martin Luther and John Calvin commemorating the 1821 union of Lutheran and Reformed churches in the Grand Duchy of Baden
Protestant Church in Hesse and Nassau (founded in 1817) is a United Protestant member church under the Protestant Church in Germany's umbrella.
Unionskirche in Idstein held by the Protestant Church in Hesse and Nassau. It commemorates the union of Lutheran and Reformed Protestants in the Duchy of Nassau in August 1817, the first of its kind and a month before the Prussian Union in September of the same year.