Like many other barrios of Malolos. Atlag has no definite and exact date of its founding. But, it can be considered one of the oldest for it was believed that it was founded in the 17th century together with the other barrios during the Spanish regime. Some historians are proclaiming that when the Filipino rebellion against Spain broke out in 1896 the barrios of Bagna and Sto. Cristo, are part of this barangay Atlag is considered a coastal area, blessed by a wide river connecting to the Manila Bay. Most of its inhabitants are fishermen, bamboo and palm trees abound the river banks.
The phrase “AT LAGI” has been associated with the barrio due to the fact that during the peak of the Spanish rebellion by the Filipinos it often times came to the knowledge of the Spanish authorities that Filipino “insurektos” hold their meeting always in this place to map out plans for their offensives against the Spaniards. So, it is a word of mouth among them “AT-LAGI” pala sila dito. But also according to other elders, the name ATLAG was derived from a name of a native tree that was grown there. According to some tales, the construction of a chapel and having St. Anthony as its patron Saint was thru the Kindness of a certain, Guillermo Dimagiba , Crisostomo or Ba Imbo to many. He is a merchant businessman in the early days. During one of his business trip, he was met by a powerful storm in the Hagonoy River in a banca. Due to the strong winds and current, his boat capsized and was driven away to the Atlag river bank. That day is June 13 the feast day of St. Anthony. So much grateful for saving his life by the residents, he constructed a chapel for them, in the site where his boat was found. It was made of native materials of bamboo and palm leaves.
Atlag is considered one of the most progressive barrio of Malolos. Its residents are successful in their own field of endeavors, in business, government service, church and civic projects. Various church and civic organizations were first established here notably Holy Name Society, Solidarity in Mary, Fatima, Adoration Nocturna. Some of its residents become priest. A more solid foundation of its economic development is the establishment of the Atlag Credit Cooperative. All these they considered blessings from God, their faith and confidence among themselves and the love of their fellow men. The barrio folks selected able and dedicated residents to lead and continue services to the church, community and to its people.
5,028 as of 2007 Source: NSO Census of Population, 2007