According to National Archives information: except for a short time during the Civil War, passports were not required for citizens traveling abroad before World War I. They were obtained however sometimes though not required because the individual believed it would afford them more protection.
National Archives has passport applications received by the Department of State with any record and forms related to it from 1791-1925. These are in Record Group 59 or Record Group 84. The applications less than 75 years old may not be used without permission.
The information contained varies; less detailed before the Civil War. It normally shows the name, signature, place of residence, age, and personal description of the applicant, names or number of persons in the family intending to travel, date, and if applicable, the date and court of naturalization. It sometimes contains the birth date of the applicant and of the spouse and children, if any, if the applicant was a naturalized citizen, the date and port of arrival in the United States, the name of the vessel on which the applicant arrived and the date and court where they were naturalized.
From 1906-1925, the application includes the name of the applicant, date and place of birth, name and date and place of birth of spouse or children (when applicable), residence and occupation at that time, immediate travel plans, physical description and a photograph. There were often letters from employers, relatives and others proving the applicant’s purpose for traveling abroad.
Applications are arranged chronologically and the main series, 1830-1925, are in bound volumes. Emergency passport applications, 1877-1905, are also in bound volumes. These applications for passports or renewals of passports were made at the U.S. Foreign Service posts abroad. They are arranged by name of post, and then chronologically. An index to the applications cite the name of the post. Emergency passport applications, 1906-25 are varied in their arrangements; there are indexes with the entries arranged alphabetically as far as the first two letters of the surname.
For some periods during 1907-25, there are separate applications for U. S. Foreign Service personnel and their dependents, military personnel and civilian government employees and their dependents, residents of Puerto Rico and the Philippine Islands, aliens who had applied for citizenship and persons who intended to visit China. These are indexed.
Other series include a register of passports issued, 1810-17; bound record copies of passports issued, 1817-34; a register of passports issued to persons destined for Santo Domingo Island 1799-1801; applications and certificates 190-25 filed at U. S. Foreign Service posts by persons who intended to stay in a particular country for an extended period of time and an index for 1907-21; also post-World War I applications for certificates of identity filed by wives of members of the American Expeditionary Forces and U. S. citizens who were residents of Germany.
There are also passport records in Archives that were maintained by diplomatic and consular posts abroad. Those records before 1874 were not always duplicated in the Department’s own files – they are for the most part scattered and have very little information.
It may be noted that Ancestry.com has most of these records on-line for viewing.