Total debt did peak as a percentage of income around 1933.
Although Federal government debt is included in this total, the Federal government total is also broken out in the blue area chart below.
Your comment below seems to reflect a misunderstanding of the chart.
This chart shows the Total Federal Debt in 2005 to be the same as that in 1950, but as a percentage of GDP to be twice as large.
The chart does show Federal goverment debt today, as a percentage of income, to be similar to the level in 1950.
Total debt on the other hand is far, far higher than it was in 1950. This is because of a dramatic rise in consumer, business, and state and local government debt since 1950.
This may not what you expected, but the chart is quite correct and is fairy straight forward.