Ed Walsh has the lowest career ERA, with an ERA of 0.43.

Interpreted as:

best with a minimum of 1500 IP pitchers with zero no hitters

	NAME	ERA	IP	NH	G	W	L	W%	GS	SO	CG	SHO	SV	H	R	HR	BB	HBP	GF	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	H/9
1	Ed Walsh E. Walsh	0.43	2015.0	1	294	140	89	.611	217	1,239	174	40	28	1,580	573	18	408	34	72		48	5.53	1.82	3.04	0.08		5.2	0.99	.252	2.56	7.06
2	George Mullin G. Mullin	0.82	1689.1	1	236	117	81	.591	195	635	150	14	3	1,645	758	27	566	67	34		33	3.38	3.02	1.12	0.14		8.5	1.31	.304	4.04	8.76
3	Nap Rucker N. Rucker	1.14	2084.1	1	299	119	122	.494	244	1,087	161	34	13	1,848	728	38	624	66	51	8,442	33	4.69	2.69	1.74	0.16	12.9	7.4	1.19	.273	3.14	7.98
4	Eddie Plank E. Plank	1.15	2338.0	0	357	173	99	.636	276	1,168	192	40	23	2,013	757	18	585	67	67		44	4.50	2.25	2.00	0.07		6.5	1.11	.276	2.91	7.75
5	Ed Willett E. Willett	1.20	1698.1	0	261	101	90	.529	194	561	136	12	5	1,630	795	24	549	105	51		61	2.97	2.91	1.02	0.13		8.2	1.28	.295	4.21	8.64
6	Jack Coombs J. Coombs	1.24	2008.2	0	308	142	91	.609	234	901	164	32	7	1,777	802	36	714	76	63		42	4.04	3.20	1.26	0.16		8.6	1.24	.263	3.59	7.96
7	Mordecai Brown M. Brown	1.27	1989.1	0	329	152	85	.641	202	869	160	31	33	1,726	669	28	418	40	117		40	3.93	1.89	2.08	0.13		5.7	1.08	.287	3.03	7.81
8	Christy Mathewson C. Mathewson	1.30	2479.2	0	340	199	93	.682	284	1,127	213	37	19	2,257	808	59	279	12	48	9,757	31	4.09	1.01	4.04	0.21	11.6	2.9	1.02	.265	2.93	8.19
9	George McQuillan G. McQuillan	1.36	1531.2	0	267	81	89	.476	168	562	100	14	17	1,363	573	23	387	29	75	6,155	15	3.30	2.27	1.45	0.14	9.1	6.3	1.14	.260	3.37	8.01
10	Chief Bender C. Bender	1.39	1857.1	1	290	136	73	.651	207	1,031	146	26	28	1,654	635	21	417	50	75		40	5.00	2.02	2.47	0.10		5.8	1.12	.285	3.08	8.01
11	Jim Scott J. Scott	1.45	1887.0	0	317	107	114	.484	226	952	122	26	9	1,628	689	21	618	56	64	7,633	32	4.54	2.95	1.54	0.10	12.5	8.1	1.19	.268	3.29	7.76
12	Cy Falkenberg C. Falkenberg	1.45	1609.1	0	236	102	81	.557	190	820	124	22	6	1,481	638	21	450	40	35		61	4.59	2.52	1.82	0.12		7.5	1.20	.313	3.57	8.28
13	Howie Camnitz H. Camnitz	1.50	1844.0	0	283	118	94	.557	215	807	119	15	13	1,663	751	41	570	58	55		30	3.94	2.78	1.42	0.20		8.0	1.21	.289	3.67	8.12
14	Ed Reulbach E. Reulbach	1.51	1927.0	0	305	127	84	.602	225	800	136	25	9	1,633	720	29	665	65	59		38	3.74	3.11	1.20	0.14		8.7	1.19	.264	3.36	7.63
15	Eddie Cicotte E. Cicotte	1.54	3200.2	1	499	208	147	.586	360	1,380	247	35	24	2,868	1,153	32	826	52	103		57	3.88	2.32	1.67	0.09		6.4	1.15	.267	3.24	8.06
16	Doc Crandall D. Crandall	1.66	1548.1	0	303	102	62	.622	134	611	91	9	25	1,536	670	52	382	40	147		8	3.55	2.22	1.60	0.30		6.6	1.24	.317	3.89	8.93
17	Walter Johnson W. Johnson	1.73	5806.1	1	788	412	270	.604	654	3,456	520	108	34	4,816	1,867	96	1,354	206	126		151	5.36	2.10	2.55	0.15		5.8	1.06	.261	2.89	7.46
18	Bob Groom B. Groom	1.86	2327.1	1	367	120	150	.444	288	1,167	157	22	11	2,207	1,079	49	783	57	46		59	4.51	3.03	1.49	0.19		8.9	1.28	.320	4.17	8.53
19	Hippo Vaughn H. Vaughn	1.92	2726.0	0	390	178	137	.565	332	1,416	214	41	5	2,463	1,038	39	803	88	48		63	4.67	2.65	1.76	0.13		7.1	1.20	.272	3.43	8.13
20	Red Ames R. Ames	1.92	2364.1	0	411	133	131	.504	274	1,115	143	20	27	2,231	981	32	692	45	98	9,751	93	4.24	2.63	1.61	0.12	11.4	7.1	1.24	.280	3.73	8.49
21	Willie Mitchell W. Mitchell	1.96	1630.0	0	276	83	92	.474	190	924	93	16	4	1,470	732	15	612	79	66		48	5.10	3.38	1.51	0.08		9.0	1.28	.280	4.04	8.12
22	Slim Sallee S. Sallee	1.96	2816.2	0	476	174	143	.549	306	835	191	25	35	2,732	1,088	66	572	43	125	11,471	12	2.67	1.83	1.46	0.21	7.3	5.0	1.17	.268	3.48	8.73
23	Ray Fisher R. Fisher	2.11	1762.2	0	278	100	94	.515	207	668	110	19	7	1,667	726	34	482	45	48	7,211	32	3.41	2.46	1.39	0.17	9.3	6.7	1.22	.273	3.71	8.51
24	Bob Harmon B. Harmon	2.21	2059.2	0	321	107	133	.446	239	644	143	15	10	1,974	961	44	764	35	61		39	2.81	3.34	0.84	0.19		8.9	1.33	.272	4.20	8.63
25	George Suggs G. Suggs	2.29	1650.2	0	246	101	89	.532	185	590	115	16	13	1,722	720	41	355	60	52		22	3.22	1.94	1.66	0.22		6.1	1.26	.352	3.93	9.39