Men's fashions did not change dramatically during the first years of the 20th century.
Knee-length overcoats, especially for driving, were popular during the ealry 1900s. Long neckties began to be worn with suits. The trousers were still straight, uncreased and uncuffed, as seen below. Also note the hat and walking stick.
Men's hair was short and typically slicked back. A center part was still common.