This is an excellent idea, I live in a city in Texas, near the corner of New Mexico. So, here's the story of Zday in Midlnd, Texas.
Zday could not have happened at a worse time for this changing city, an economic boom was drawing people in by the thousands, but the infrastructure had not yet had time to adjust. The news of the virus had arrived long before the actual disease had. Some people spent thousands of dollars on equipment and food stockpiles in preperation, others did nothing. About 3 weeks after the first news reports of zed, the first undead were found in Midland, a couple in their apartment. They were killed (again) and disposed of without further infection. This incident sparked panic, there were many false reports of infected individuals, a general distrust took root in the scared citizens. For about a week there were no more known incidents, but the nearby city of Odessa was begining to see the first signs of outbreak. Midland police and medical teams were sent to Odessa to assist in slowing the infected. The Midland hospital took in patients from Odessa, many of whom were bitten. Soon the hospital was at capicity, and waiting rooms filled with infected, and eventually, undead. People who were bitten hid their bites for fear of being killed by their fellow citizens out of fear and panic. When word got out that undead were spilling out from the hospital, people rioted, looters and scared citizens all took to the streets at once. With many personell still in Odessa, there weren't enough recources to deal with the undead, let alone the rioters. Even in their miniscule numbers, the undead were able to wreak havoc thanks to the chaos around them. Thousands were bitten during the rioting, while vigilante groups executed the bitten they could find, almost all escaped to their homes, where they turned. Eventually the riots dispursed and everyone went home, many to prepare for leaving. The next day, almost the whole surviving population, bitten and non-infected, attempted to leave the city. The massive number of cars far surpassed the ablity of the roads to move them, and it took hours to even reach the interstate. Alerted by the sound of engines, undead poured out of homes in huge numbers. When they reached the major roads, people did everything they could to escape in a massive free for all, but only succeeded in making it harder to escape. Some people became trapped in their cars, most fled on foot, nearly all were killed or bitten. Now it was almost a matter of time untill nearly the whole city was undead, less than 2 weeks since the first undead appeeared, the city was lost to zed. Most of the survivors (mostly individuals), found their way home, and attempted to dig in and wait it out. When food and water ran out, they were forced to leave their homes, the first scavengers. Originally, nearly all survivors were hostle to one another, occasionally banding together for a common goal, but permanent groups were rare. Now, over a year since Zday, an alliance of many small groups is attempting to reclaim the city, and is even securing strips of the interstate outside of the city. There are quarrels between groups occasionally, but overall, there is little inter-fighting. The group still encounters lone survivors who are hostile towards them, and handles them with little tollerance. With diligent fighting and teamwork, the city of Midland may one day become a beacon of hope to a forsaken world, but untill that day comes, survivors will work hard to secure the city peice by peice.