▁the ▁copy right ed ▁musical ▁compos itions ▁of ▁its ▁members . ▁ ▁April – J une ▁▁ ▁April ▁ 9 ▁– ▁T amp ico ▁Aff air , ▁involving ▁U . S . ▁Navy ▁sail ors ▁in ▁Mexico . ▁ ▁April ▁ 1 1 ▁– ▁Al pha ▁R ho ▁Chi , ▁a ▁professional ▁architecture ▁frat ern ity , ▁is ▁founded ▁in ▁the ▁Hotel ▁Sh erman ▁in ▁Chicago . ▁ ▁April ▁ 1 4 ▁– ▁The ▁city ▁of ▁Ir ving , ▁Texas , ▁is ▁incorpor ated . ▁ ▁April ▁ 2 0 ▁ ▁Lud low ▁Mass acre ▁( Color ado ▁Co al field ▁War ▁( 1 9 1 3 – 1 4 )): ▁The ▁Colorado ▁National ▁Guard ▁attacks ▁a ▁tent ▁col ony ▁of ▁ 1 , 2 0 0 ▁striking ▁coal ▁min ers ▁in ▁Lud low , ▁Colorado , ▁killing ▁ 2 4 ▁people . ▁ ▁President ▁Wood row ▁Wilson ▁asks ▁Congress ▁to ▁use ▁military ▁force ▁in ▁Mexico ▁in ▁reaction ▁to ▁the ▁T amp ico ▁Aff air . ▁ ▁April ▁ 2 1 ▁– ▁United ▁States ▁occupation ▁of ▁Ver ac ru z : ▁ 2 , 3 0 0 ▁U . S . ▁Navy ▁sail ors ▁and ▁Mar ines ▁from ▁the ▁South ▁Atlantic ▁fleet ▁land ▁in ▁the ▁port ▁city ▁of ▁Ver ac ru z , ▁Mexico , ▁which ▁they ▁will ▁occup y ▁for ▁over ▁ 6 ▁months . ▁The ▁Y p ir anga ▁incident ▁occurs ▁when ▁they ▁attempt ▁to ▁en force ▁an ▁arms ▁embargo ▁against ▁Mexico ▁by ▁prevent ing ▁the ▁German ▁cargo ▁ste amer ▁