Short answers, pulled from the story.
Texas officially seceded from the Union on the 1st of February 1861 when the state legislature passed an Ordinance of Secession by a vote of 166 to 7. A statewide referendum held on the 23rd of February affirmed this decision with 46,129 votes for approval and 14,697 against it.
Lieutenant Governor Edward Clark replaced Sam Houston as governor after state officials declared his office vacant following his refusal to swear loyalty to the Confederacy. This occurred after Houston remained silent when his name was called three times at the convention.
Confederate soldiers under Lt. Colin D. McRae attacked a band of German Texans in a bend of the Nueces River resulting in approximately 19 Unionists killed in fighting. After the battle, 9 to 11 wounded Unionists were murdered with shots to the head in what became known as the Nueces Massacre.
The Battle of Palmito Ranch took place in Texas on the 12th of May 1865 serving as the final engagement of the war. This event occurred well after General Robert E. Lee surrendered at Old Appomattox Court House on the 9th of April 1865.
Federal troops arrived in Texas to restore order on the 19th of June 1865 when Union Maj. Gen. Gordon Granger and 2,000 Union soldiers took possession of the state. The Stars and Stripes were not raised over Austin until June 25 following this arrival.