Innate around Bochnia, Poland on January 27, 1861 to Gustav Sinnmayer Modrzejewski and actress Helena Modrzejewska. His father died withwithin 1865 & in 1868 his mother married Count Bozenta Chlapowski. Together it immigrated to United states of america around July, 1876, where his mother changed her title to "Helena Modjeska" and her son's title to "Ralph Modjeski". Modjeski returned to Europe to learn at " "L'Ecole des Ponts et Chaussees" in Paris, France, where he graduated in 1885 at the top of his class. He married the same year, to Felicie Benda (the couple had three children). He later married Virginia Mary Giblyn.

He returned to America to begin his career, working on projects in several states. In 1895 he opened his own office. His first project as a chief engineer was the railroad bridge across the Mississippi River at Rock Island, Illinois. During his career he served as chief or consulting engineer on dozens of bridges across the country.

He took over the mis-designed Quebec Bridge after the 1907 disaster killed that 75 workers, and succeeded in creating the longest truss span in the world (though a construction accident killed another 10 workers). It is still the longest cantilevered bridge in the world.

He died June 26, 1940 in Los Angeles, California. He was considered as "United states's greatest bridge builder" and received many awards and honorary degrees. Notable among them is the John Fritz Medal in 1930. Notable projects
Chief Engineer Thebes Bridge Benjamin Franklin Bridge Tacony-Palmyra Bridge San Francisco-Oakland Bay Bridge Blue Water Bridge

Consulting Engineer Ambassador Bridge Manhattan Bridge