The question we get most about lawns is 'sod or seed?' The honest answer is that both work in Maryland if the ground is prepared properly and the timing is right, and both fail if it isn't.
Timing first. Mid-August through early October is the best window in Carroll County for tall fescue, which is the grass that handles our heat, cold, and partial shade best. The soil is warm, nights are cooling off, and the weeds that choke a spring seeding have mostly quit for the year. Spring is the second-best window. Summer is the worst.
Sod gives you a finished lawn the same day and can be laid most of the growing season if you keep it watered. It costs more, but it's the right call on slopes that would wash out under seed, and for anyone who needs a usable yard now. Seed costs a fraction as much and fills in over a season, which is fine on flat ground when you can wait.
Either way, the work that decides whether the lawn takes happens before any grass goes down: killing off or stripping what's there, fixing the grade so water doesn't pool, adding screened topsoil where the clay is close to the surface, and raking a smooth seedbed. Skip that and you'll be reseeding the same thin patches every spring.
If you're planning a new lawn in Westminster, Hampstead, Mount Airy, or anywhere nearby, get on the calendar before August. Fall fills up fast.