US Government spending as percent of GDP

Before WW1, government spending accounted for around 10% of GDP in the US
After end of WW2, it was around 20%
Since then, it has grown to almost 40%
This includes federal, state, and municipal spending
A large chunk of the federal spending is social security, which is basically a transfer payment. Arguably that should be in a special category.
A funny side note, the Wikipedia article gives California its own section on this page. It is the only state with this distinction.