He was a partner at the firm Carter Ledyard & Milburn, personal counsel to J.P. Morgan, and a president of the New York City Bar Association.

His paternal grandparents were Benjamin Ledyard (1779–1812), a prominent New York attorney, and Susan French (née Livingston) (1789–1864).

[1] His niece, Matilda Cass Ledyard (1871–1960), married Baron Clemens von Ketteler (1853–1900), a German diplomat.

[5] He matriculated at Columbia College in 1868, but transferred after his freshman year to Harvard, where he received his Bachelor of Arts degree in 1872.

Following the passage of the Sherman Antitrust Act in 1890, Ledyard became a prominent adviser to the steel, petroleum, and tobacco industries.

[9] In 1903, Ledyard also oversaw the passage of a bill in the New York State Legislature requiring the electrification of the rail lines at Grand Central Station following a deadly train collision in 1902.

The bill and subsequent improvements resulted in the covering of the railroad tracks outside the station, the extension of Park Avenue, and the expansion of valuable real estate in the surrounding area.

[10] In addition to his professional career, Ledyard was a prominent figure in New York society and civic life.

[7] In 1914, he became a member of the New Hampshire Society of the Cincinnati by right of his descent from Captain Jonathan Cass who served during the American Revolution.