In the eighth year of Xianfeng in Qing dynasty (1858), six forts were built to strengthen coastal defense and ensure the safety of both capital city. Three of them are on the south bank and two are on the north bank, gradually forming a complete defense system with "power, town, sea, gate and height" as the main body. Since modern times, with the invasion of China by foreign powers, Dagu Lake area has become a military stronghold in the north. During the sixty years from 1840 to 1900, foreign powers invaded Dagukou four times in order to gain economic interests and political privileges in China. Relying on "building a strong ship and sharpening guns", they put Dagu area under the ravages of its iron hoof, and even advanced on Beijing, burning the Yuanmingyuan, which is known as the palace of oriental art, forcing the Qing rulers to leave Beijing twice. The soldiers and civilians in Dagu Lake area fought to the death with the invading enemy, which showed the indomitable, brave and strong national spirit of the Chinese nation. 190 1 year, the Qing government was forced to demolish Dagukou Fort according to the "Xin Chou Treaty" which humiliated the country, and now only three "Hai" Fort and Fort Sites are left in the south bank.

After liberation, Dagukou Fort Site was officially designated as a national key cultural relics protection unit by the State Council, named as one of the "Ten Scenes of Jinmen", with the reputation of "Haimen ancient fortress", and was also designated as a patriotic education base in Tianjin. Haimen Bridge and Dagu Lighthouse adjacent to Dagukou have also become tourist attractions.