alternatehistory.com

11 May

The Passaic and the Casco are launched in Pittsburgh, both ironclads constructed in a city not connected to the Eastern Seaboard and as such not caught in the slipyard by Milne's forces.
While the Passaic (renamed after the destruction of the original on the slips) is a serviceable ship that is essentially a straight upgrade on Monitor (and slated to be armed with a 15" Rodman gun as soon as one becomes available later in the summer), the Casco's launch is seriously problematic. For unknown reasons, the problems discovered at Erie were not communicated to Pittsburgh, and the Casco has barely three inches of freeboard when unarmed and uncoaled - indeed, the waves produced by her own launching nearly swamp her.

Pennefeather enters Detroit. He will leave behind Canadian militia units to garrison the city and secure his line of communication, and push west for Grand Rapids.

12 May
The Prince Consort launches at Pembroke. Originally a 91-gun second rate, she has been converted on the stocks to an ironclad and will mount 24 68-lber guns and 9 Armstrong 110-lber guns, with her belt and battery armour being of similar construction to that of the Warrior. Much work has been done on her insides on the slips, and she is expected to enter commission late in the year.

Also on this date, the French la Gloire arrives off Veracruz. She begins bombardment of San Juan de Ulúa with three steam frigates and one battleship in support - with the British fully engaged in attempting to bring the United States to surrender by way of coastal attack, Napoleon III wants to demonstrate French prowess.

13 May

Six mortar gunboats arrive off the Eastern Seaboard. Milne is not sure what to do with them, as he has already in fact done most of the work without the use of mortar ships, but spreads them out and assigns two to the Great Lakes instead.
As he is seeing to this, one of the sloops with his force (the paddle wheeler Styx) orders a potential blockade runner to heave-to. Taking advantage of his speed against the wind, Styx's captain stops and searches the American merchant vessel, the Golden Eagle. The ship, a clipper, claims to be carrying a cargo of non-contraband silk and tea, but Styx's captain orders a full search - and discovers two thousand Belgian rifles concealed under the floor.
This cargo is a large enough consignment that Milne has Golden Eagle sent to Halifax with a prize crew (and the escort of a gunboat) for the courts to determine whether the whole ship is forfeit.