When and why women left the labour market? It is well documented that women in now developed countries entered the labour market all thoughout the 20th century. As such, female labour participation have consistently increased. For example, this is a table from Godin (1977):



Here is a graph from a more  recent report:



However, I have the impression that the feudal, or pre-capitalist societies, which were mainly agrarian and textile based, relied heavily on female labour. We can probably all picture housewives working in the field or sawing textiles.

So, the question is, when and why women left the labour market? Is this because of a transition from feudalism toward a capitalistic mode of production? Or the shift from agriculture to industry?
They worked at home. Like "Household Engineers" do today, doing everything working from down to dusk like their husbands, and like their husband they shared in the earnings of the household.
Until the industrial revolution came each household operated like a mini business.  

It was the Industrial revolution that divided "work"(e.g. business) from home.

They never left the workforce, They just stopped being called the workforce.

Ironically with people working from home more and more we are returning to such a system.