Samut Prakan was built as a frontier town to protect the approach to Bangkok further up-river. Its importance grew due to its stragic position at the river mouth. Walls were built along the river and forts were built at various locations. Many of these are now in a very dilapidated state or have been built over. However, a few remain in a good state and along the river bank on both sides are cannons left over from this period.

The six main forts are as follows:

1. Phra Chulachomklao Fort (in good condition and open to the public)
2. Plaeng Faifah Fort (now a park in Phra Pradaeng)
   
3. Phi Sua Samut Fort (can be seen on the island between Paknam Market and Phra Samut Chedi)
   
4. Nakarat Fort
   
5. Pracone Chai Fort