The Lego Duplo brand and the first duplo brick appeared in 1969.The duplo bricks were available in four colours. They are red, blue, yellow and white. On the next year, two more sets were added with red and blue wheel plates. The product catalog in 1971,the sets were targeted at children from 1 to 2 years old but were still mixed with the Lego bricks designed normally for kids from 3 to 12 years. Bricks with 2 rows of 2 studs was then introduced in 1972.
In 1975, duplo became its own product brand with five sets made up exclusively of Duplo bricks. New additions was included a round-topped 2by2 stud brick and a small 4 wheel wagon with two rows of 6 studs. Then, Lego Duplo was targeting children 1 and a half years with the idea that when the children reached 3, Duplo bricks could be used together with Lego bricks.
The Duplo name was dropped by the favor of Lego Preschool in the year 1977. Cylindrical head and tapered body without limbs was also introduced. The new bricks are the half arch bricks and 2 by 6 knobs wagon. The 2 by 6 wagon can be joined together which can be joined together which can be used as a long car or a train.
The name Duplo, was brought back in 1979 with a new reworked logo. Bricks were often came inside a plush version of the rabbit that zipped close.
In 1983 , Duplo people appeared with movable head, arms and legs and looks like large minifigures but, it cannot be taken apart for safer handling by small children. Also in 1983, set number 2700 was introduced amudel of a steam engine with two train cars.
A Duplo dollhouse with sliding doors was introduced in 1986. The Duplo dollhouse came with a Duplo people mother, father and child. In 1992, Duplo Toolo was introduced which used internal screws to stay together. In 1993, gray rail train system with a stop and start track was introduced with two more train system. In 2005, Lego sell Duplo trains themed as Thomas the Tank Engine.
In 2002, the name Duplo was dropped again and was replaced with Lego Explore. In the spring 2004, the catalog was with a reminder that Lego Duplo was exchanged with Lego explore. However that fall, the name Duplo was back again with a new rabbit logo to match the Lego Quatro range. Lego currently makes Duplo licensed with Bob the Builder and Thomas and Friends. Nowadays, there are Farm, Zoo, Town, Castle and even pirate lines. Dollhouse and princess castle are introduced since 2008.