Both men were from Scotland and the Taylor family believes they knew each other before they left there.
"When they met in Sydney, they hatched a plan to sail to New Zealand."
When they arrived in Whanganui, they built a jetty and store on Taupō Quay and began trading goods and passengers nationally and internationally.
Taylor said the Taylor and Watt Company soon became an "incredibly important part of the European economy".
"Over the life of the company they sailed 13 ships, including one which made a single voyage from Whanganui to Southhampton, England, direct.
"As well as being the leading maritime business, they were leading bankers for the first couple of decades of the city's life and the largest landowners in Whanganui."
Taylor still farms on part of the land that his great-great-grandfather bought.
Watt and Taylor were also pivotal in starting the Presbyterian church in Whanganui and when Taylor died in 1871, while taking a ship across Cook Strait in a storm, the shops in Whanganui were closed for four days as a mark of respect.
In 1881 William Hogg Watt became Whanganui's first mayor.
The Taylor and Watt window will be the 23rd stained glass window in the council chamber. An invitation-only unveiling will be held in October and the Havelock North-based great-great-grandson of William Hogg Watt hopes to attend the ceremony, Taylor said.
The public will be able to view the stained glass windows during Whanganui Heritage Month. The council chamber will be open for two free guided tours on October 3 and October 10.
The aim of the stained glass windows project is to reflect and celebrate the events, people and places that make up the story of the district, from early Māori history to the modern day. There is space for nine more stained glass windows.
To ensure each panel meets the aims of the project, the concept goes through a process of checks with community arts co-ordinator Anique Jayasinghe, mayor Hamish McDouall, designer Julie Greig and glass artist Greg Hall before work begins.
People or organisations who have a local story to tell and are interested in sponsoring a window can contact Anique Jayasinghe on 349 3086 or 021 268 4881.