Booker was the son of Thomas Booker and his wife Rhoda, and was baptised at St Botolph's Aldgate on 23 July 1824. Between 1844 and 1848, Booker travelled in Asia, Southern Europe, the United States and Canada. Attracted by Colonel Mason's report on the discovery of gold in California, he left England on 17 January 1849 for Chagres, then the chief Atlantic port on the Isthmus of Panama. After a three-week wait in Panama City, he then travelled north on board a clipper to San Francisco, arriving at the end of June 1849.