Rubuta ci gaba ga wannan sakin layi - Bayan samun digiri na farko na zane-zane, Donovan ya yi shekaru biyu a Makarantar Koyon Shari'a ta Columbia, inda ya kasance abokin aji na Franklin D. Roosevelt, kuma ya yi karatu a karkashin Harlan Fiske Stone. Da ya koma Buffalo, ya shiga kamfanin lauya mai daraja na Love & Keating a 1909 kuma, bayan shekaru biyu, ya buɗe kamfaninsa na Buffalo tare da abokin aikinsa na Columbia, Bradley Goodyear. A shekara ta 1914, kamfaninsu ya haɗu da wani, ya zama Goodyear & O'Brien. A cikin 1912, Donovan ya taimaka ya kafa, kuma ya zama shugaban, rundunar sojan doki na New York National Guard. An tattara wannan rukunin a shekarar 1916 kuma ya yi aiki a kan iyakar Amurka da Mexico yayin yakin da gwamnatin Amurka ta yi da Pancho Villa
Ka yi haƙuri. Ya yi nazarin dabarun soji da dabarun yaƙi. Ya kuma dauki darussan wasan kwaikwayo a Birnin New York daga wani tauraron wasan kwaikwayo na rana, Eleanor Robson. A shekara ta 1914, ya auri Ruth Rumsey, magajin Buffalo wanda ya halarci Rosemary Hall.