[2] She remained with the firm and worked on bridges and other infrastructure projects in Scotland,[4] becoming a corporate member of the Institution of Civil Engineers in 1939.

[13] She was awarded an honorary Doctor of Science degree at Heriot-Watt University in 1985,[14] for her work in encouraging women to take up engineering careers.

[1] At a celebration of Fergusson's life, the Dean of the Faculty of Engineering at Heriot-Watt University, Clephane Hume remarked she was "A memorable lady, with a terrific sense of humour".

A portrait of Fergusson was unveiled in June 2015 in the William Arrol building at Heriot-Watt University, where a Hall of residence is named after her.

[15] National Grid named a 510 tonne, 160-metre-long tunnel boring machine "Mary" after Fergusson, in honour of her status as the first female fellow of the Institution of Civil Engineers.