Although the exact date of its discovery is unknown, the antiquity of its inhabitants is a clear fact. In 14th century, the century when Bilbao was founded, a document proves that the labourers (taxpayers), inhabitants of the labourer´s houses of Galdakao "anteiglesia" (together with other "anteiglesias": San Juan de Bedia, Arrigorriaga, Zarátamo and San Miguel de Basauri), asked the Infant Don Juan, Lord of Biscay, to defend them against the abuse they were subjected to by some Elderly Relations.
On 12 march 1375 they were conceded the privilege through a document dated in Almanzán and Galdakao became annexed to Bilbao until 1630.
Undoubtedly it is known since 16th century that Galdakao "anteiglesia", belonging to the district of Uribe, occupied the seat number 38 in the General Assembly of Biscay, under two faithful governors, in addition to the open council or "cruz parada" to settle the most important agreements.
Its old church, Santa Maria de Ganguren after the mountain Ganguren(demolished in 1782), stood in a very isolated place. In 13th century Santa María of Elexalde rose in its place. Its founder, Sancho de Galdácano and Torrezábal.
Galdakao took part in several conflicts as the Convention War(1795), the Napoleonic War (1808-1812) and the First Carlist War (1833-1839). Thus, Galdakao played an important role in the latter. The history shows that "the casa consistorial (town hall) served as headquarters for the carlists for a long time during the Civil War". Until the end of the conflict, Galdakao was a military post of the carlist troops.
With the revolution of industry in 19th century, Galdakao had already iniciated since the remote times: quarries, iron ores, well-known refractory stones of Abusua. It palyed a major role in industries, later largely benefited from the railway inauguration (San Sebastián-Bilbao, 1882) crossing the borough, initially called Biscay Central Railway.
The setting up of the Dynamite Factory (1872) together with other important firms as the melting factory in Usansolo or the mineral fertilizers in Guturribai. A process that has led to a demographic boom up to now.
During the Civil War (1936), Galdako remained in the hands of the Republic troops until 15 june 1937. Aprotection wall called "Cinturón de Hierro de Bilbao" was erected arround. The Dynamite Factory was bombed during the months May and June by the national air force. Consecuently, by the time the First Brigade of Navarre seized the town, after defeating the batallions of the Basque Government, the dynamite factory had already been severely hit suffering important damage.
The post-war period and its consequent reppresion led to an economic, social and cultural crisis; nevertheless, its continuous growth has given rise to aprogressive town-planning.
Currently, its population is 30.000 inhabitants, as planned by the "Plan General de Ordenación Urbana" (General Town Planning), passed in 1993 by the Town Council. This Plan tries to combine the different sectors: agriculture, industry and amenities with leisure and the different areas of the place; an aim in order to enjoy a prosperous and nice borough.