Sidney Hayden, Jr., was born in Sayre, Pennsylvania, on February 15, 1857, to Sidney Hayden and Florilla Miller. His father was a farmer and brick maker who owned at least $10,000 in real estate by 1850. Hayden attended common school in Sayre before completing his education at academies in Athens, Pennsylvania, and Waverly, New York. He studied law in Waverly in the late 1870s, and in 1879, he moved to Holton, Kansas. He earned admission to the bar soon afterward and formed a law partnership with his brother Charles. As one writer observed, he “practiced extensively before the state Supreme court, the federal Circuit, District and Court of Appeals, and has been admitted to practice before the Supreme Court of the United States.”
Hayden married Mary Walker around 1880, and they had two children: Charles and Helen. He joined the Democratic Party and spent many years on the county and state Democratic committees. He ran unsuccessfully for a seat in the state senate in 1882, and he was the Democratic nominee for state attorney general a year later. He served as a Democratic presidential elector in 1896 and carried Kansas’s official election returns to Washington, D.C.
Hayden died in Holton on February 15, 1907, after a short struggle with pleuro-pneumonia.