Over the past 15 months, Adler Tank Rentals has entered seven new U.S. markets. We are continuing to execute in building out our national footprint to support higher rental revenue and earnings levels in the years ahead. This is all by design. However, our tank and box rental business is not without its blemishes related to rapid growth, as reflected in our higher expenses over the past few quarters. The sooner we can ramp and establish our tank and box rental business in all of the key domestic markets, the faster Adler Tank Rentals can contribute on a more meaningful level to McGrath RentCorp's overall earnings.
Modular division rental revenues for the quarter decreased by 3%, or $0.6 million, from a year ago to $19.3 million. Rental revenues grew by 6% quarter over quarter in our markets outside of California and declined by 10% within the state. Modular division rental revenues outside of California now represent approximately 47% of total modular rental revenues. First month's modular building rental bookings for the division increased 37% from a year ago, with bookings outside of California increasing 68% and staying fairly flat within the state. Our Texas and Florida modular building business activity has been very favorable over the first four months of 2013. Many of these modular building rental bookings are for classrooms and larger custom commercial complexes that tend to have longer rental terms, and will not begin billing until the second and third quarters of 2013. Although we have not seen the healthier California economy over the past few quarters reflected in our modular results to date, we are hopeful that we are nearing an inflection point in our California results. Modular division quarter over quarter income from operations decreased by approximately 28% to $2.9 million from $4.0 million in 2012. In addition to lower rental revenues for the quarter, inventory center labor and material expenses were higher from a year ago due to processing a larger number of custom projects, classrooms for late spring and summer shipments and overall higher commercial business activity levels.