Not really: there were billionaires back then as well (the first billionaire was Rockefeller in 1916.) By the CPI, $1 in 1920 would be about $14 in 2021. Nomina

Not really: there were billionaires back then as well (the first billionaire was Rockefeller in 1916.) By the CPI, $1 in 1920 would be about $14 in 2021. Nominal (non-real) GDP was around $900 nominal per capita. So a millionaire then would be have one thousand times the per capita GDP. Per capita GDP in 2020 was $63k, so as a multiple of per-capita GDP a millionaire would have $63 million. So a 1920s millionaire is the equivalent of somewhere between $14M and $63M today.