Economic commentator Peter Schiff, nicknamed Dr. Doom for his prediction of the 2008 economic crisis , wrote in the Wall Street Journal about the so-called 91% tax rate of the 1950’s. The rate applied to very, very few and due to deductions, was paid by nearly no one.  The article is linked below and is free, no paywall.
I quote excerpts below:
Liberal pundits point out that in the 1950s, when America’s economic might was at its zenith, the rich faced tax rates as high as 91%. True enough, the top marginal income-tax rate in the 1950s was much higher than today’s top rate of 35%—but the share of income paid by the wealthiest Americans has essentially remained flat since then.
In 1958, the top 3% of taxpayers earned 14.7% of all adjusted gross income and paid 29.2% of all federal income taxes. In 2010, the top 3% earned 27.2% of adjusted gross income and their share of all federal taxes rose proportionally, to 51%.
So if the top marginal tax rate has fallen to 35% from 91%, how in the world has the tax burden on the wealthy remained roughly the same? … Lower- and middle-income workers now bear a significantly lighter burden than in the past. And the confiscatory top marginal rates of the 1950s were essentially symbolic—very few actually paid them.
In 1958, an 81% marginal tax rate applied to incomes above $140,000, and the 91% rate kicked in at $400,000 for couples. These figures are in unadjusted 1958 dollars and correspond today to nominal income levels that are about eight times higher. That year, according to Internal Revenue Service records, about 10,000 of the nation’s 45.6 million tax filers had income that was taxed at 81% or higher.
In 1958, approximately two million filers (4.4% of all taxpayers) earned the $12,000 or more for married couples needed to face marginal rates as high as 30%. These Americans paid about 35% of all income taxes. And now? In 2010, 3.9 million taxpayers (2.75% of all taxpayers) were subjected to rates that were 33% or higher. These Americans—many of whom would hardly call themselves wealthy—reported an adjusted gross income of $209,000 or higher, and they paid 49.7% of all income taxes.
In contrast, the share of taxes paid by the bottom two-thirds of taxpayers has fallen dramatically over the same period. In 1958, these Americans accounted for 41.3% of adjusted gross income and paid 29% of all federal taxes. By 2010, their share of adjusted gross income had fallen to 22.5%. But their share of taxes paid fell far more dramatically—to 6.7%…
In 1958, even the lowest-tier filers, which included everyone making up to $5,000 annually, were subjected to an effective 20% rate. Today, almost half of all tax filers have no income-tax liability whatsoever, and many “taxpayers” actually get a net refund from the government. Those nostalgic for 1950s-era “tax fairness” should bear this in mind.
The tax code of the 1950s allowed upper-income Americans to take exemptions and deductions that are unheard of today. Tax shelters were widespread, and not just for the superrich. The working wealthy—including doctors, lawyers, business owners and executives—were versed in the art of creating losses to lower their tax exposure.
For instance, a doctor who earned $50,000 through his medical practice could reduce his taxable income to zero with $50,000 in paper losses or depreciation from property he owned through a real-estate investment partnership. Huge numbers of professionals signed up for all kinds of money-losing schemes. Today, a corresponding doctor earning $500,000 can deduct a maximum of $3,000 from his taxable income, no matter how large the loss.
When Ronald Reagan finally lowered rates in the 1980s, he did so in exchange for scrapping uneconomical deductions.
It’s hard to determine how much otherwise taxable income disappeared through tax shelters in the 1950s. As a result, direct comparisons between the 1950s and now are difficult. However, it is worth noting that from 1958 to 2010, the taxes paid by the top 3% of earners, as a percentage of total personal income (which can’t be reduced by shelters), increased to 3.96% from 2.72%, while the percentage paid by the bottom two-thirds of filers fell to 0.51% in 2010 from 2.7%. This starker division of relative tax burdens can be explained by the inability of upper-income groups to shelter income.
1950s pictures from Wikipedia Commons.
 http://www.webcitation.org/5oz96pIPX (Fortune: “Peter Schiff: Oh, he saw it coming.” Brian O’Keefe, January 23, 2009.